http://coloradoriverscience.org/api.php?action=feedcontributions&feedformat=atom&user=JeffreyJLukascoloradoriverscience.org - User contributions [en]2026-07-25T15:26:50ZUser contributionsMediaWiki 1.43.0http://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4569Wildfire and water2026-07-23T19:43:25Z<p>JeffreyJLukas: /* Overview */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> In general, recent wildfires have also spread faster, burned at higher overall severity, and burned at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention<ref name="broxton2025" /><ref name="lumbrazo2026" /> and may modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors.<ref name="goeking2020" /><ref name="goeking2022" /> Several water providers, including [https://storymaps.arcgis.com/stories/6ef2af96207046baa8451cf20def46cb Denver Water] and [https://www.srpnet.com/grid-water-management/water-management/watershed Salt River Project], have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality.<ref name="gillespie2026" /> These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity.<ref name="beechie2010" /> <br />
<br />
Many PBR projects in the basin are supported by water agencies, in collaboration with land managers and environmental NGOs. For example, the [https://www.kvcollab.org/ Kawuneeche Valley Restoration Collaborative] (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
<br />
==Additional resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes.<br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<ref name="broxton2025">Broxton, P. D., Biederman, J. A., Dwivedi, R., Van Leeuwen, W. J. D., Sankey, T. Ts., Woolley, T., & Svoma, B. M. (2025). Forest Patch Geometry and Climate Regulate the Impact of Forest Thinning on Snowpack in the Southwest United States. Ecohydrology, 18(6), e70111. https://doi.org/10.1002/eco.70111</ref><br />
<br />
<ref name="goeking2020">Goeking, S. A., & Tarboton, D. G. (2020). Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests. Journal of Forestry, 118(2), 172–192. https://doi.org/10.1093/jofore/fvz069</ref><br />
<br />
<ref name="goeking2022">Goeking, S. A., & Tarboton, D. G. (2022). Variable Streamflow Response to Forest Disturbance in the Western US: A Large‐Sample Hydrology Approach. Water Resources Research, 58(6), e2021WR031575. https://doi.org/10.1029/2021WR031575</ref><br />
<br />
<ref name="lumbrazo2026">Lumbrazo, C., Howe, E. R., Dickerson-Lange, S. E., Pestana, S., Cramblitt, J., Dedinsky, K., Smith, K., & Lundquist, J. D. (2026). Can we maximize snow storage through fire-resilient forest treatments? Insights from experimental forest treatments in the Eastern Cascades, WA, USA. Frontiers in Forests and Global Change, 8, 1707812. https://doi.org/10.3389/ffgc.2025.1707812</ref><br />
<br />
<ref name="gillespie2026">Gillespie, N.; Adams, P.; Croft, J.; Flitcroft, R.; Hogervorst, J.; Powers, P., & Callery, D. (2026). Integrating watershed restoration in wildfire management: opportunities, approaches, and examples. Washington, DC: U.S. Department of Agriculture, Forest Service, Washington Office. 20 p. https://www.fs.usda.gov/sites/default/files/fs_media/fs_document/watershed-restoration-in-wildfire.pdf</ref><br />
<br />
<ref name="beechie2010">Beechie, Timothy J.; Sear, David A.; Olden, Julian D.; Pess, George R.; Buffington, John M.; Moir, Hamish; Roni, Philip, & Pollock, Michael M. (2010). Process-based principles for restoring river ecosystems. BioScience. 60(3): 209-222. https://research.fs.usda.gov/download/treesearch/34786.pdf</ref> <br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4568Wildfire and water2026-07-23T19:36:25Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention<ref name="broxton2025" /><ref name="lumbrazo2026" /> and may modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors.<ref name="goeking2020" /><ref name="goeking2022" /> Several water providers, including [https://storymaps.arcgis.com/stories/6ef2af96207046baa8451cf20def46cb Denver Water] and [https://www.srpnet.com/grid-water-management/water-management/watershed Salt River Project], have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality.<ref name="gillespie2026" /> These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity.<ref name="beechie2010" /> <br />
<br />
Many PBR projects in the basin are supported by water agencies, in collaboration with land managers and environmental NGOs. For example, the [https://www.kvcollab.org/ Kawuneeche Valley Restoration Collaborative] (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
<br />
==Additional resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes.<br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
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<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
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<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
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<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<ref name="broxton2025">Broxton, P. D., Biederman, J. A., Dwivedi, R., Van Leeuwen, W. J. D., Sankey, T. Ts., Woolley, T., & Svoma, B. M. (2025). Forest Patch Geometry and Climate Regulate the Impact of Forest Thinning on Snowpack in the Southwest United States. Ecohydrology, 18(6), e70111. https://doi.org/10.1002/eco.70111</ref><br />
<br />
<ref name="goeking2020">Goeking, S. A., & Tarboton, D. G. (2020). Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests. Journal of Forestry, 118(2), 172–192. https://doi.org/10.1093/jofore/fvz069</ref><br />
<br />
<ref name="goeking2022">Goeking, S. A., & Tarboton, D. G. (2022). Variable Streamflow Response to Forest Disturbance in the Western US: A Large‐Sample Hydrology Approach. Water Resources Research, 58(6), e2021WR031575. https://doi.org/10.1029/2021WR031575</ref><br />
<br />
<ref name="lumbrazo2026">Lumbrazo, C., Howe, E. R., Dickerson-Lange, S. E., Pestana, S., Cramblitt, J., Dedinsky, K., Smith, K., & Lundquist, J. D. (2026). Can we maximize snow storage through fire-resilient forest treatments? Insights from experimental forest treatments in the Eastern Cascades, WA, USA. Frontiers in Forests and Global Change, 8, 1707812. https://doi.org/10.3389/ffgc.2025.1707812</ref><br />
<br />
<ref name="gillespie2026">Gillespie, N.; Adams, P.; Croft, J.; Flitcroft, R.; Hogervorst, J.; Powers, P., & Callery, D. (2026). Integrating watershed restoration in wildfire management: opportunities, approaches, and examples. Washington, DC: U.S. Department of Agriculture, Forest Service, Washington Office. 20 p. https://www.fs.usda.gov/sites/default/files/fs_media/fs_document/watershed-restoration-in-wildfire.pdf</ref><br />
<br />
<ref name="beechie2010">Beechie, Timothy J.; Sear, David A.; Olden, Julian D.; Pess, George R.; Buffington, John M.; Moir, Hamish; Roni, Philip, & Pollock, Michael M. (2010). Process-based principles for restoring river ecosystems. BioScience. 60(3): 209-222. https://research.fs.usda.gov/download/treesearch/34786.pdf</ref> <br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4567Wildfire and water2026-07-23T16:35:40Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention<ref name="broxton2025" /><ref name="lumbrazo2026" /> and may modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors.<ref name="goeking2020" /><ref name="goeking2022" /> Several water providers, including [https://storymaps.arcgis.com/stories/6ef2af96207046baa8451cf20def46cb Denver Water] and [https://www.srpnet.com/grid-water-management/water-management/watershed Salt River Project], have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the [https://www.kvcollab.org/ Kawuneeche Valley Restoration Collaborative] (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
<br />
==Additional resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes.<br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<ref name="broxton2025">Broxton, P. D., Biederman, J. A., Dwivedi, R., Van Leeuwen, W. J. D., Sankey, T. Ts., Woolley, T., & Svoma, B. M. (2025). Forest Patch Geometry and Climate Regulate the Impact of Forest Thinning on Snowpack in the Southwest United States. Ecohydrology, 18(6), e70111. https://doi.org/10.1002/eco.70111</ref><br />
<br />
<ref name="goeking2020">Goeking, S. A., & Tarboton, D. G. (2020). Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests. Journal of Forestry, 118(2), 172–192. https://doi.org/10.1093/jofore/fvz069</ref><br />
<br />
<ref name="goeking2022">Goeking, S. A., & Tarboton, D. G. (2022). Variable Streamflow Response to Forest Disturbance in the Western US: A Large‐Sample Hydrology Approach. Water Resources Research, 58(6), e2021WR031575. https://doi.org/10.1029/2021WR031575</ref><br />
<br />
<ref name="lumbrazo2026">Lumbrazo, C., Howe, E. R., Dickerson-Lange, S. E., Pestana, S., Cramblitt, J., Dedinsky, K., Smith, K., & Lundquist, J. D. (2026). Can we maximize snow storage through fire-resilient forest treatments? Insights from experimental forest treatments in the Eastern Cascades, WA, USA. Frontiers in Forests and Global Change, 8, 1707812. https://doi.org/10.3389/ffgc.2025.1707812</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4566Wildfire and water2026-07-23T16:34:20Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention<ref name="broxton2025" /><ref name="lumbrazo2026" /> and may modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors.<ref name="goeking2020" /><ref name="goeking2022" /> Several water providers, including [https://storymaps.arcgis.com/stories/6ef2af96207046baa8451cf20def46cb Denver Water] and [https://www.srpnet.com/grid-water-management/water-management/watershed Salt River Project], have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
<br />
==Additional resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes.<br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<ref name="broxton2025">Broxton, P. D., Biederman, J. A., Dwivedi, R., Van Leeuwen, W. J. D., Sankey, T. Ts., Woolley, T., & Svoma, B. M. (2025). Forest Patch Geometry and Climate Regulate the Impact of Forest Thinning on Snowpack in the Southwest United States. Ecohydrology, 18(6), e70111. https://doi.org/10.1002/eco.70111</ref><br />
<br />
<ref name="goeking2020">Goeking, S. A., & Tarboton, D. G. (2020). Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests. Journal of Forestry, 118(2), 172–192. https://doi.org/10.1093/jofore/fvz069</ref><br />
<br />
<ref name="goeking2022">Goeking, S. A., & Tarboton, D. G. (2022). Variable Streamflow Response to Forest Disturbance in the Western US: A Large‐Sample Hydrology Approach. Water Resources Research, 58(6), e2021WR031575. https://doi.org/10.1029/2021WR031575</ref><br />
<br />
<ref name="lumbrazo2026">Lumbrazo, C., Howe, E. R., Dickerson-Lange, S. E., Pestana, S., Cramblitt, J., Dedinsky, K., Smith, K., & Lundquist, J. D. (2026). Can we maximize snow storage through fire-resilient forest treatments? Insights from experimental forest treatments in the Eastern Cascades, WA, USA. Frontiers in Forests and Global Change, 8, 1707812. https://doi.org/10.3389/ffgc.2025.1707812</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4565Wildfire and water2026-07-23T16:33:42Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention<ref name="broxton2025" /><ref name="lumbrazo2026" /> and may modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors.<ref name="goeking2020" /><ref name="goeking2022" /> Several water providers, including Denver Water ([https://storymaps.arcgis.com/stories/6ef2af96207046baa8451cf20def46cb Forests to Faucets]) and [https://www.srpnet.com/grid-water-management/water-management/watershed Salt River Project], have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
<br />
==Additional resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes.<br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<ref name="broxton2025">Broxton, P. D., Biederman, J. A., Dwivedi, R., Van Leeuwen, W. J. D., Sankey, T. Ts., Woolley, T., & Svoma, B. M. (2025). Forest Patch Geometry and Climate Regulate the Impact of Forest Thinning on Snowpack in the Southwest United States. Ecohydrology, 18(6), e70111. https://doi.org/10.1002/eco.70111</ref><br />
<br />
<ref name="goeking2020">Goeking, S. A., & Tarboton, D. G. (2020). Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests. Journal of Forestry, 118(2), 172–192. https://doi.org/10.1093/jofore/fvz069</ref><br />
<br />
<ref name="goeking2022">Goeking, S. A., & Tarboton, D. G. (2022). Variable Streamflow Response to Forest Disturbance in the Western US: A Large‐Sample Hydrology Approach. Water Resources Research, 58(6), e2021WR031575. https://doi.org/10.1029/2021WR031575</ref><br />
<br />
<ref name="lumbrazo2026">Lumbrazo, C., Howe, E. R., Dickerson-Lange, S. E., Pestana, S., Cramblitt, J., Dedinsky, K., Smith, K., & Lundquist, J. D. (2026). Can we maximize snow storage through fire-resilient forest treatments? Insights from experimental forest treatments in the Eastern Cascades, WA, USA. Frontiers in Forests and Global Change, 8, 1707812. https://doi.org/10.3389/ffgc.2025.1707812</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4564Wildfire and water2026-07-23T16:19:06Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention<ref name="broxton2025" /><ref name="lumbrazo2026" /> and may modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors.<ref name="goeking2020" /><ref name="goeking2022" /> Several water providers, including Denver Water ([[https://storymaps.arcgis.com/stories/6ef2af96207046baa8451cf20def46cb Forests to Faucets]]) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
<br />
==Additional resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes.<br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<ref name="broxton2025">Broxton, P. D., Biederman, J. A., Dwivedi, R., Van Leeuwen, W. J. D., Sankey, T. Ts., Woolley, T., & Svoma, B. M. (2025). Forest Patch Geometry and Climate Regulate the Impact of Forest Thinning on Snowpack in the Southwest United States. Ecohydrology, 18(6), e70111. https://doi.org/10.1002/eco.70111</ref><br />
<br />
<ref name="goeking2020">Goeking, S. A., & Tarboton, D. G. (2020). Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests. Journal of Forestry, 118(2), 172–192. https://doi.org/10.1093/jofore/fvz069</ref><br />
<br />
<ref name="goeking2022">Goeking, S. A., & Tarboton, D. G. (2022). Variable Streamflow Response to Forest Disturbance in the Western US: A Large‐Sample Hydrology Approach. Water Resources Research, 58(6), e2021WR031575. https://doi.org/10.1029/2021WR031575</ref><br />
<br />
<ref name="lumbrazo2026">Lumbrazo, C., Howe, E. R., Dickerson-Lange, S. E., Pestana, S., Cramblitt, J., Dedinsky, K., Smith, K., & Lundquist, J. D. (2026). Can we maximize snow storage through fire-resilient forest treatments? Insights from experimental forest treatments in the Eastern Cascades, WA, USA. Frontiers in Forests and Global Change, 8, 1707812. https://doi.org/10.3389/ffgc.2025.1707812</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4563Wildfire and water2026-07-23T16:16:20Z<p>JeffreyJLukas: /* Additional Resources */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention<ref name="broxton2025" /><ref name="lumbrazo2026" /> and may modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors.<ref name="goeking2020" /><ref name="goeking2022" /> Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
<br />
==Additional resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes.<br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<ref name="broxton2025">Broxton, P. D., Biederman, J. A., Dwivedi, R., Van Leeuwen, W. J. D., Sankey, T. Ts., Woolley, T., & Svoma, B. M. (2025). Forest Patch Geometry and Climate Regulate the Impact of Forest Thinning on Snowpack in the Southwest United States. Ecohydrology, 18(6), e70111. https://doi.org/10.1002/eco.70111</ref><br />
<br />
<ref name="goeking2020">Goeking, S. A., & Tarboton, D. G. (2020). Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests. Journal of Forestry, 118(2), 172–192. https://doi.org/10.1093/jofore/fvz069</ref><br />
<br />
<ref name="goeking2022">Goeking, S. A., & Tarboton, D. G. (2022). Variable Streamflow Response to Forest Disturbance in the Western US: A Large‐Sample Hydrology Approach. Water Resources Research, 58(6), e2021WR031575. https://doi.org/10.1029/2021WR031575</ref><br />
<br />
<ref name="lumbrazo2026">Lumbrazo, C., Howe, E. R., Dickerson-Lange, S. E., Pestana, S., Cramblitt, J., Dedinsky, K., Smith, K., & Lundquist, J. D. (2026). Can we maximize snow storage through fire-resilient forest treatments? Insights from experimental forest treatments in the Eastern Cascades, WA, USA. Frontiers in Forests and Global Change, 8, 1707812. https://doi.org/10.3389/ffgc.2025.1707812</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4562Wildfire and water2026-07-23T16:15:58Z<p>JeffreyJLukas: /* Data and Tools */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention<ref name="broxton2025" /><ref name="lumbrazo2026" /> and may modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors.<ref name="goeking2020" /><ref name="goeking2022" /> Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
<br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<ref name="broxton2025">Broxton, P. D., Biederman, J. A., Dwivedi, R., Van Leeuwen, W. J. D., Sankey, T. Ts., Woolley, T., & Svoma, B. M. (2025). Forest Patch Geometry and Climate Regulate the Impact of Forest Thinning on Snowpack in the Southwest United States. Ecohydrology, 18(6), e70111. https://doi.org/10.1002/eco.70111</ref><br />
<br />
<ref name="goeking2020">Goeking, S. A., & Tarboton, D. G. (2020). Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests. Journal of Forestry, 118(2), 172–192. https://doi.org/10.1093/jofore/fvz069</ref><br />
<br />
<ref name="goeking2022">Goeking, S. A., & Tarboton, D. G. (2022). Variable Streamflow Response to Forest Disturbance in the Western US: A Large‐Sample Hydrology Approach. Water Resources Research, 58(6), e2021WR031575. https://doi.org/10.1029/2021WR031575</ref><br />
<br />
<ref name="lumbrazo2026">Lumbrazo, C., Howe, E. R., Dickerson-Lange, S. E., Pestana, S., Cramblitt, J., Dedinsky, K., Smith, K., & Lundquist, J. D. (2026). Can we maximize snow storage through fire-resilient forest treatments? Insights from experimental forest treatments in the Eastern Cascades, WA, USA. Frontiers in Forests and Global Change, 8, 1707812. https://doi.org/10.3389/ffgc.2025.1707812</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4561Wildfire and water2026-07-23T16:14:54Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention<ref name="broxton2025" /><ref name="lumbrazo2026" /> and may modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors.<ref name="goeking2020" /><ref name="goeking2022" /> Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<ref name="broxton2025">Broxton, P. D., Biederman, J. A., Dwivedi, R., Van Leeuwen, W. J. D., Sankey, T. Ts., Woolley, T., & Svoma, B. M. (2025). Forest Patch Geometry and Climate Regulate the Impact of Forest Thinning on Snowpack in the Southwest United States. Ecohydrology, 18(6), e70111. https://doi.org/10.1002/eco.70111</ref><br />
<br />
<ref name="goeking2020">Goeking, S. A., & Tarboton, D. G. (2020). Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests. Journal of Forestry, 118(2), 172–192. https://doi.org/10.1093/jofore/fvz069</ref><br />
<br />
<ref name="goeking2022">Goeking, S. A., & Tarboton, D. G. (2022). Variable Streamflow Response to Forest Disturbance in the Western US: A Large‐Sample Hydrology Approach. Water Resources Research, 58(6), e2021WR031575. https://doi.org/10.1029/2021WR031575</ref><br />
<br />
<ref name="lumbrazo2026">Lumbrazo, C., Howe, E. R., Dickerson-Lange, S. E., Pestana, S., Cramblitt, J., Dedinsky, K., Smith, K., & Lundquist, J. D. (2026). Can we maximize snow storage through fire-resilient forest treatments? Insights from experimental forest treatments in the Eastern Cascades, WA, USA. Frontiers in Forests and Global Change, 8, 1707812. https://doi.org/10.3389/ffgc.2025.1707812</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4560Wildfire and water2026-07-23T16:14:34Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention <ref name="broxton2025" /><ref name="lumbrazo2026" />and may modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors.<ref name="goeking2020" /><ref name="goeking2022" /> Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<ref name="broxton2025">Broxton, P. D., Biederman, J. A., Dwivedi, R., Van Leeuwen, W. J. D., Sankey, T. Ts., Woolley, T., & Svoma, B. M. (2025). Forest Patch Geometry and Climate Regulate the Impact of Forest Thinning on Snowpack in the Southwest United States. Ecohydrology, 18(6), e70111. https://doi.org/10.1002/eco.70111</ref><br />
<br />
<ref name="goeking2020">Goeking, S. A., & Tarboton, D. G. (2020). Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests. Journal of Forestry, 118(2), 172–192. https://doi.org/10.1093/jofore/fvz069</ref><br />
<br />
<ref name="goeking2022">Goeking, S. A., & Tarboton, D. G. (2022). Variable Streamflow Response to Forest Disturbance in the Western US: A Large‐Sample Hydrology Approach. Water Resources Research, 58(6), e2021WR031575. https://doi.org/10.1029/2021WR031575</ref><br />
<br />
<ref name="lumbrazo2026">Lumbrazo, C., Howe, E. R., Dickerson-Lange, S. E., Pestana, S., Cramblitt, J., Dedinsky, K., Smith, K., & Lundquist, J. D. (2026). Can we maximize snow storage through fire-resilient forest treatments? Insights from experimental forest treatments in the Eastern Cascades, WA, USA. Frontiers in Forests and Global Change, 8, 1707812. https://doi.org/10.3389/ffgc.2025.1707812</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4559Wildfire and water2026-07-23T16:07:21Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain and dependent on many local factors. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=MediaWiki:Sidebar&diff=4558MediaWiki:Sidebar2026-07-23T15:14:50Z<p>JeffreyJLukas: </p>
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<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more opportunities for ignition during periods of high fire danger.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4556Wildfire and water2026-07-23T14:58:52Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="poon2018" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4554Wildfire and water2026-07-16T22:18:12Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="alizadeh2021" /><ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression.<ref name="stephens2012" /><ref name="davis2024" /> These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<ref name="davis2024">Davis, K. T., Peeler, J., Fargione, J., Haugo, R. D., Metlen, K. L., Robles, M. D., & Woolley, T. (2024). Tamm review: A meta-analysis of thinning, prescribed fire, and wildfire effects on subsequent wildfire severity in conifer dominated forests of the Western US. Forest Ecology and Management, 561, 121885. https://doi.org/10.1016/j.foreco.2024.121885</ref><br />
<br />
<ref name="stephens2012">Stephens, S. L., McIver, J. D., Boerner, R. E. J., Fettig, C. J., Fontaine, J. B., Hartsough, B. R., Kennedy, P. L., & Schwilk, D. W. (2012). The Effects of Forest Fuel-Reduction Treatments in the United States. BioScience, 62(6), 549–560. https://doi.org/10.1525/bio.2012.62.6.6</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4553Wildfire and water2026-07-16T21:20:08Z<p>JeffreyJLukas: /* Overview */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="alizadeh2021" /><ref name="mcgrath2023" /><ref name="kampf2022" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4552Wildfire and water2026-07-16T21:19:18Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2021" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<ref name="parks2020" /><ref name="boisrame2022" /><ref name="higuera2023" /><br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<ref name="boisrame2022">Boisramé, G. F. S., Brown, T. J., & Bachelet, D. M. (2022). Trends in western USA fire fuels using historical data and modeling. Fire Ecology, 18(1), 8. https://doi.org/10.1186/s42408-022-00129-4</ref><br />
<br />
<ref name="higuera2023">Higuera, P. E., Cook, M. C., Balch, J. K., Stavros, E. N., Mahood, A. L., & St. Denis, L. A. (2023). Shifting social-ecological fire regimes explain increasing structure loss from Western wildfires. PNAS Nexus, 2(3), pgad005. https://doi.org/10.1093/pnasnexus/pgad005</ref><br />
<br />
<ref name="parks2020">Parks, S. A., & Abatzoglou, J. T. (2020). Warmer and Drier Fire Seasons Contribute to Increases in Area Burned at High Severity in Western US Forests From 1985 to 2017. Geophysical Research Letters, 47(22). https://doi.org/10.1029/2020GL089858</ref><br />
<br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4551Wildfire and water2026-07-16T20:41:22Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year.<ref name="williams2025" /> Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s.<ref name="parks2023" /><ref name="alizadeh2023" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="alizadeh2023">Alizadeh, M. R., Abatzoglou, J. T., Adamowski, J., Modaresi Rad, A., AghaKouchak, A., Pausata, F. S. R., & Sadegh, M. (2023). Elevation-dependent intensification of fire danger in the western United States. Nature Communications, 14(1), 1773. https://doi.org/10.1038/s41467-023-37311-4</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4550Wildfire and water2026-07-16T20:40:57Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year<ref name="williams2025" />. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. <ref name="parks2023" /><ref name="alizadeh2023" /> In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<ref name="alizadeh2023">Alizadeh, M. R., Abatzoglou, J. T., Adamowski, J., Modaresi Rad, A., AghaKouchak, A., Pausata, F. S. R., & Sadegh, M. (2023). Elevation-dependent intensification of fire danger in the western United States. Nature Communications, 14(1), 1773. https://doi.org/10.1038/s41467-023-37311-4</ref><br />
<br />
<ref name="parks2023">Parks, S. A., Holsinger, L. M., Blankenship, K., Dillon, G. K., Goeking, S. A., & Swaty, R. (2023). Contemporary wildfires are more severe compared to the historical reference period in western US dry conifer forests. Forest Ecology and Management, 544, 121232. https://doi.org/10.1016/j.foreco.2023.121232</ref><br />
<br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4549Wildfire and water2026-07-16T20:37:33Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year<ref name="williams2025" />. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
<ref name="williams2025">Williams, A. P., Juang, C. S., & Short, K. C. (2025). The Western United States MTBS-Interagency database of large wildfires, 1984–2024 (WUMI2024a). Earth Syst. Sci. Data, 17(12), 7359–7372. https://doi.org/10.5194/essd-17-7359-2025</ref><br />
<br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4548Wildfire and water2026-07-16T20:34:39Z<p>JeffreyJLukas: /* Overview */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds (Table 1, below), from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4547Wildfire and water2026-07-16T15:47:18Z<p>JeffreyJLukas: /* Water quality impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among these contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4546Wildfire and water2026-07-16T15:46:06Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4545Wildfire and water2026-07-16T15:44:16Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and thus overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, when necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4544Wildfire and water2026-07-16T15:43:50Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and thus overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, where necessary, earthmoving to reestablish natural channels and stream connectivity. <br />
<br />
PBR projects in the basin are often supported by water agencies in collaboration with land managers and environmental NGOs. For example, the Kawuneeche Valley Restoration Collaborative (KVRC) in the Colorado River headwaters in north-central Colorado receives direct funding and staff involvement from Northern Water as well as grants from the Colorado Water Conservation Board, Colorado River District, and Reclamation.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4543Wildfire and water2026-07-16T15:35:02Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and thus overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
More recently, it has been recognized that stream and wetland restoration can bring substantial co-benefits for wildfire mitigation. Restoring the water- and sediment-retention functions of riparian and wetland areas and enlarging their footprint on the landscape can slow fire spread through "wet fuel breaks", reduce burn severity, and alleviate post-fire impacts on water quality. These restoration techniques, collectively called process-based restoration (PBR), include beaver reintroduction, emplacing logs and wood structures in stream channels such as beaver-dam analogs (BDAs), riparian plantings, meadow restoration, and, where necessary, earthmoving to reestablish natural channels and stream connectivity.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4542Wildfire and water2026-07-15T20:42:14Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and thus overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire have been used for many years to reduce the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
Wetland and stream restoration can slow fire spread, and reduce burn severity, while also creating fire breaks and safe zones for wildfire firefighters.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4541Wildfire and water2026-07-15T20:37:05Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and thus overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of high-severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
Wetland and stream restoration can slow fire spread, and reduce burn severity, while also creating fire breaks and safe zones for wildfire firefighters.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4540Wildfire and water2026-07-15T20:13:25Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and thus overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain. Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
Additional management strategies to reduce the spread and/or intensity of wildfires<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4539Wildfire and water2026-07-15T20:10:55Z<p>JeffreyJLukas: /* Land management to reduce fire risk and impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and thus overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires, particularly in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4538Wildfire and water2026-07-15T20:09:20Z<p>JeffreyJLukas: /* Forest Treatments */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and thus overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Land management to reduce fire risk and impacts===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4537Wildfire and water2026-07-15T20:08:51Z<p>JeffreyJLukas: /* Soil infiltration and runoff */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and thus overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
====Soil infiltration and runoff====<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Forest Treatments===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4536Wildfire and water2026-07-15T20:08:39Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, plant water use, soil infiltration, and thus overall runoff efficiency, and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Water supply impacts===<br />
<br />
====Snowpack and timing of snowmelt and runoff====<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
====Plant water use====<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
===Soil infiltration and runoff===<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Forest Treatments===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4535Wildfire and water2026-07-15T20:05:22Z<p>JeffreyJLukas: /* Water Quality Impacts */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, transpiration from vegetation, soil infiltration, and thus overall runoff efficiency (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Snowpack and timing of snowmelt and runoff===<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
===Vegetation water use===<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
===Soils===<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water quality impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Forest Treatments===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4534Wildfire and water2026-07-15T20:05:06Z<p>JeffreyJLukas: /* Vegetation and Evaporation Changes */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, transpiration from vegetation, soil infiltration, and thus overall runoff efficiency (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Snowpack and timing of snowmelt and runoff===<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
===Vegetation water use===<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
===Soils===<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water Quality Impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Forest Treatments===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4533Wildfire and water2026-07-15T20:04:35Z<p>JeffreyJLukas: /* Overview */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, transpiration from vegetation, soil infiltration, and thus overall runoff efficiency (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Snowpack and timing of snowmelt and runoff===<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
===Vegetation and Evaporation Changes===<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
===Soils===<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water Quality Impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Forest Treatments===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4532Wildfire and water2026-07-15T20:00:47Z<p>JeffreyJLukas: /* Overview */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. Overall, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, many large high-severity wildfires have impacted runoff-generating watersheds, from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, runoff efficiency, and soil infiltration and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted the basin's water resources. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Snowpack and timing of snowmelt and runoff===<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
===Vegetation and Evaporation Changes===<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
===Soils===<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water Quality Impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Forest Treatments===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4531Wildfire and water2026-07-14T19:23:48Z<p>JeffreyJLukas: /* Overview */</p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, West-wide average annual burned area has more than doubled, and the number of "megafires" (>100,000 acres) has increased from about one per year to over five per year. In general, wildfires are also spreading faster, burning at higher overall severity, and at higher average elevations than in the 1980s and 1990s. In the Colorado River Basin, large and severe wildfires since 2000 have impacted runoff-generating watersheds from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity in the past several decades have multiple causes, including warming and drying of the atmosphere and vegetation due to anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and many more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, runoff efficiency, and soil infiltration and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted water resources in the Colorado River Basin. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Snowpack and timing of snowmelt and runoff===<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
===Vegetation and Evaporation Changes===<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
===Soils===<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water Quality Impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Forest Treatments===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4530Wildfire and water2026-07-14T19:02:56Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, average annual burned area has more than doubled, with many more very large fires (>10,000 acres) that are burning at higher overall severity than in the 1980s and 1990s. In the Colorado River Basin, large and severe wildfires since 2000 have impacted runoff-generating watersheds from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of Arizona (Figure 1) and New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity since the 1980s have multiple causes, including warming and drying of the atmosphere and vegetation with anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, runoff efficiency, and soil infiltration and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted water resources in the Colorado River Basin. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Snowpack and timing of snowmelt and runoff===<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
===Vegetation and Evaporation Changes===<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
===Soils===<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water Quality Impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Forest Treatments===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Wildfire_and_water&diff=4529Wildfire and water2026-07-14T17:55:17Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
[[File:DragonBravoFire.jpg|thumb|600px|Figure 1. Smoke plume from the Dragon Bravo Fire over the Grand Canyon on July 11, 2025. (Photo: National Park Service/M. Quinn)]]<br />
<br />
Watersheds across the western United States are being increasingly impacted by wildfires. Since 2000, annual burned area has increased several-fold West-wide, with many more very large fires (>10,000 acres) that are burning at higher overall severity than in the 1980s and 1990s. In the Colorado River Basin, large and severe wildfires since 2000 have impacted runoff-generating watersheds from the subalpine spruce-fir and lodgepole forests of Colorado, Utah, and Wyoming, to the ponderosa pine and mixed-conifer forests of the Mogollon Rim and White Mountains and the Gila Wilderness in New Mexico.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="alizadeh2021" /><br />
The dramatic shifts in wildfire occurrence and severity since the 1980s have multiple causes, including warming and drying of the atmosphere and vegetation with anthropogenic climate change, increases in fuel loading and forest density from past forest uses and fire suppression, and increases in development in the wildland-urban interface (WUI) and in wildland recreation, leading to additional structural fuels and more ignition opportunities.<br />
<br />
Wildfires can affect the basin's water resources and complicate their management in two interrelated ways: (1) altering water supply by changing snowpack accumulation and timing, runoff efficiency, and soil infiltration and (2) impairing water quality by mobilizing sediment, organic carbon, metals, and nutrients into the stream. Preventative forest management (e.g., fuels mitigation) can be undertaken to reduce wildfire impacts. These forest treatments can themselves affect watershed hydrology, depending on their intensity and scale.<br />
<br />
===Notable recent wildfires in the Colorado River Basin===<br />
<br />
The table below summarizes selected large wildfires since 2000 that have impacted water resources in the Colorado River Basin. <br />
<br />
'''Table 1. Selected Large Wildfires in the Colorado River Basin since 2000'''<br />
<br />
{| class="wikitable"<br />
! Fire<br />
! Year<br />
! Size (acres)<br />
! Location<br />
! Water-related impacts<br />
|-<br />
| Wallow<br />
| 2011<br />
| 538,049<br />
| White Mountains, Arizona (Salt River)<br />
| Altered summer streamflow, high peak flows and flood events, water quality impacts.<br />
|-<br />
| Rodeo–Chediski<br />
| 2002<br />
| 468,638<br />
| White Mountains/Mogollon Rim, Arizona (Salt River)<br />
| Changes in evapotranspiration in previously forested areas; elevated nitrogen (N), phosphorus (P), arsenic (As), lead (Pb), copper (Cu), and iron (Fe) documented in the Salt River at Roosevelt Lake.<br />
|-<br />
| Whitewater–Baldy<br />
| 2012<br />
| 297,845<br />
| Gila National Forest, New Mexico (Gila River)<br />
| Stream degradation and debris flows in the Gila River following the fire; destruction of native Gila trout habitat.<br />
|-<br />
| East Troublesome<br />
| 2020<br />
| 193,812<br />
| Grand County, Colorado (Colorado River)<br />
| Sediment and debris flows, harmful algal blooms, increased water treatment demands, and elevated peak runoff following precipitation events.<br />
|-<br />
| Dragon–Bravo<br />
| 2025<br />
| 145,504<br />
| North Rim, Grand Canyon, Arizona (Colorado River)<br />
| Reduced water supply by approximately 50%; destroyed the North Rim's only potable water system; post-fire debris flows.<br />
|-<br />
| Grizzly Creek<br />
| 2020<br />
| 32,632<br />
| Glenwood Canyon, Colorado (Colorado River)<br />
| High turbidity following the fire; debris flows blocked the mainstem Colorado River channel.<br />
|-<br />
| Dollar Ridge<br />
| 2018<br />
| 68,869<br />
| Strawberry River, Utah<br />
| Debris flows and total dissolved solids (TDS) transported into the Strawberry River and Starvation Reservoir; changes in TDS and pH impaired the fishery.<br />
|-<br />
| East Fork<br />
| 2020<br />
| 89,765<br />
| Duchesne River, Utah<br />
| Debris flows, damage to water lines at Moon Lake Campground, and high total dissolved solids (TDS) influxes.<br />
|}<br />
<br />
===Snowpack and timing of snowmelt and runoff===<br />
<br />
Wildfires can alter the amount and timing of streamflows primarily by impacting the accumulation and melt of the seasonal snowpack. Large wildfires that kill some portion of the canopy (i.e., crown fire) consistently result in decreased snow-water storage and earlier timing of snowmelt.<ref name="smoot2021" /><ref name="giovando2022" /><ref name="koshkin2022" /> The loss of forest canopy alters the snowpack energy balance by increasing solar radiation reaching the snow surface, causing enhanced melt and sublimation throughout the winter and spring.<ref name="mcgrath2023" /><ref name="kampf2022" /><ref name="smoot2021" /><ref name="koshkin2022" /> Additionally, black carbon and burned woody debris shed onto the snow post-fire darkens its surface, causing greater absorption of solar radiation and accelerating melt rates.<ref name="mcgrath2023" /><ref name="koshkin2022" /><ref name="smoot2021" /><ref name="kampf2022" /> These changes in snow accumulation and melt timing are long-lived<ref name="mcgrath2023" />, persisting for at least 10 years<ref name="smoot2021" /><ref name="koshkin2022" /><ref name="giovando2022" />, and need to be factored into for water supply forecasting, planning, and management.<br />
<br />
===Vegetation and Evaporation Changes===<br />
<br />
By causing both immediate and delayed mortality in non-woody plants, shrubs, and trees wildfires typically result in reductions to total water use (i.e., transpiration) by vegetation in the burn area.<ref name="bar2019" /><ref name="niccoli2023" /><ref name="obrien2010" /> The timing of onset, magnitude, and duration of these changes depend strongly on burn severity, vegetation type, and forest recovery mechanisms. During the period that transpiration is reduced, runoff from the burned area may increase, depending on the fire's effects on other elements of the area's water balance.<br />
<br />
Reduced transpiration following wildfire vegetation mortality has been documented across many forest types.<ref name="dore2012" /><ref name="nolan2014" /><ref name="poon2018" /><ref name="cooper2019" /><ref name="ma2020" /> The duration of these reductions varies, but typically lasts from 2 to 15 years.<ref name="hausler2018" /><ref name="ma2020" /><ref name="dore2012" /> In some cases, vigorous regrowth of trees post-fire ultimately leads to greater water use than in the pre-fire condition.<ref name="langford1975" /><ref name="kuczera1987" /><ref name="buckley2012" /><ref name="meili2024" /><br />
<br />
===Soils===<br />
<br />
Wildfires also often change how water from rain and snowmelt moves through–or doesn't move through–the soil. Fires strip away the protective and water-absorbent surface litter layer, exposing bare soil, and reduce tree canopy cover that could have prevented raindrops from directly striking that soil.<ref name="wine2016" /> High-severity fires can also create a strongly water-repellent (hydrophobic) layer beneath the surface.<ref name="mataix2004" /><ref name="huffman2001" /><ref name="shakesby2006" /> This hydrophobic layer inhibits rain and snowmelt from soaking into the soil, so that more of that water reaches the stream through surface runoff rather than slower groundwater processes.<ref name="wine2016" /><ref name="williams2022" /><ref name="koshkin2022" /><ref name="beeson2001" /> This leads to more abrupt and higher peak stream discharges after snowmelt and rain events, with much higher risk for damaging flash floods and debris flows, and potentially also to increases in total annual water yield, depending on other factors.<ref name="wine2016" /><br />
<br />
===Water Quality Impacts===<br />
<br />
After a wildfire, large areas of soil are newly exposed to erosion. The resulting jump in sediment flux to streams and rivers, along with ash and other burned debris, causes many contaminants to exceed pre-fire concentrations by orders of magnitude.<ref name="paul2022" /> Among those contaminants is dissolved organic carbon (DOC), which can combine with the chlorine used in water treatment to form harmful chlorinated by-products such as trihalomethanes (THMs) and haloacetic acids (HAAs).<ref name="smith2011" /><ref name="hohner2019" /> while also reducing coagulation efficiency in treatment plants.<ref name="hohner2019" /><ref name="hohner2017" /><br />
<br />
Levels of nutrients such as nitrogen (N) and phosphorus (P) can also spike.<ref name="paul2022" /> causing algal blooms and other biological impacts.<ref name="paul2022" /><ref name="hohner2019" /> Metals such as iron (Fe), manganese (Mn), arsenic (As), lead (Pb), and copper (Cu) are often mobilized with the sediment and ash as well.<ref name="smith2011" /><ref name="burton2016" /><ref name="allen2005" /><ref name="kelly2006" /> While most of these water-chemistry impacts subside within five years of a wildfire, some effects, such as the persistence of nitrogen and DOC, can extend for 15 years or more following high-severity events.<ref name="hohner2019" /><ref name="paul2022" /><br />
<br />
Beyond the chemical contaminants, the dramatically increased sediment loading in streams and rivers is itself problematic for water treatment.<ref name="paul2022" /><ref name="smith2011" /> High turbidity makes disinfection and filtration less efficient and more costly.<ref name="smith2011" /><ref name="paul2022" /><ref name="emelko2011" /> and in extreme conditions water intakes may have to be shut down completely.<ref name="hohner2019" /><ref name="writer2014" /><ref name="paul2022" /> The influx of ash and sediment also has acute effects on aquatic life.<ref name="earl2003" /><ref name="paul2022" /> often leading to declines in fish populations.<ref name="paul2022" /><ref name="rust2019" /> The altered physical and chemical conditions post-fire can drive shifts in macroinvertebrate communities towards more opportunistic species.<ref name="paul2022" /><br />
<br />
===Forest Treatments===<br />
<br />
Mechanical thinning and prescribed fire can lower the risk of future high severity fires in mid-elevation ponderosa pine and mixed-conifer forests that have become much denser due to post-1900 fire suppression. These treatments can also improve snowpack retention and modestly increase annual streamflow by reducing canopy interception and evapotranspiration, though sustained increases in water supply from such treatments are uncertain.<br />
<br />
Several water providers, including Denver Water (Forests to Faucets) and Salt River Project (SRP Healthy Forests Initiative), have partnered with land managers to plan, fund, and carry out forest treatments in their Colorado River Basin watersheds to reduce the risk of severe wildfires and their impacts to water supplies.<br />
<br />
==Data and Tools==<br />
<br />
<onlyinclude><br />
===[https://lcms-viewer.fs2c.usda.gov/mtbs USDA MTBS (Burn Severity) Data Explorer]===<br />
Monitoring Trends in Burn Severity (MTBS) is an interagency program to map the burn severity and extent of large wildfires (>1,000 acres in the West) based on satellite imagery. When opened, the MTBS Data Explorer will show the perimeter and per-pixel burn severity of all large fires from 1984 through 2024. To see the name, ignition date, and acreage of a fire, select Tools > Pixel Tools > Query Visible Map Layers and then click within a fire perimeter. <br />
<br />
===[https://egp.wildfire.gov/maps/incidents NIFC WildfireSA Public Map]===<br />
This interactive map from the National Interagency Fire Center (NIFC) shows all current and recent wildfires (‘incidents’). Click on a fire to bring up more information about that fire. From the Layers button in the upper right, you can also select ‘Fuels Treatments’ to show all recent (>2000) management actions to reduce fuels. <br />
<br />
===[https://apps.usgs.gov/landslides/pwfdf/ USGS Post-Fire Debris Flow Hazard Assessment Viewer]===<br />
The USGS produces rapid postfire debris-flow hazard assessments for select fires in the Western U.S., using geospatial data on basin slopes, burn severity, soil properties, and rainfall characteristics to estimate the likelihood and volume of debris flows that may occur in response to a defined rainstorm (typically 0.25”-0.5” in 15 minutes, corresponding to a once-in-1-year event).<br />
</onlyinclude><br />
==Additional Resources==<br />
<br />
===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===<br />
<br />
This 2025 review paper by Ebel et al. synthesizes existing research on how wildfire alters hydrologic processes and streamflow generation in the western United States. It presents a narrative review and conceptual model highlighting the key factors that shape post-fire changes in streamflow such as seasonal precipitation, the timing overlap between precipitation and potential evapotranspiration, shifts in interception and evapotranspiration relative to overall precipitation, and vegetation-related changes. <br />
<br />
==Notes==<br />
<references><br />
<ref name="mcgrath2023">McGrath, D., Zeller, L., Bonnell, R., Reis, W., Kampf, S., Williams, K., ... & Rittger, K. (2023). ''Declines in peak snow water equivalent and elevated snowmelt rates following the 2020 Cameron Peak wildfire in northern Colorado.'' Geophysical Research Letters, 50(6), e2022GL101294.</ref><br />
<br />
<ref name="kampf2022">Kampf, S. K., McGrath, D., Sears, M. G., Fassnacht, S. R., Kiewiet, L., & Hammond, J. C. (2022). ''Increasing wildfire impacts on snowpack in the western US.'' Proceedings of the National Academy of Sciences, 119(39), e2200333119.</ref><br />
<br />
<ref name="alizadeh2021">Alizadeh, M. R., Abatzoglou, J. T., Luce, C. H., Adamowski, J. F., Farid, A., & Sadegh, M. (2021). Warming enabled upslope advance in western US forest fires. Proceedings of the National Academy of Sciences, 118(22), e2009717118.</ref><br />
<br />
<ref name="smoot2021">Smoot, E. E., & Gleason, K. E. (2021). ''Forest fires reduce snow-water storage and advance the timing of snowmelt across the Western US.'' Water, 13(24), 3533.</ref><br />
<br />
<ref name="giovando2022">Giovando, J., & Niemann, J. D. (2022). ''Wildfire impacts on snowpack phenology in a changing climate within the western US.'' Water Resources Research, 58(8), e2021WR031569.</ref><br />
<br />
<ref name="koshkin2022">Koshkin, A. L., Hatchett, B. J., & Nolin, A. W. (2022). ''Wildfire impacts on western United States snowpacks.'' Frontiers in Water, 4, 971271.</ref><br />
<br />
<ref name="bar2019">Bär, A., Michaletz, S. T., & Mayr, S. (2019). ''Fire effects on tree physiology.'' New Phytologist, 223(4), 1728–1741.</ref><br />
<br />
<ref name="niccoli2023">Niccoli, F., Pacheco-Solana, A., Delzon, S., et al. (2023). ''Effects of wildfire on growth, transpiration and hydraulic properties of Pinus pinaster Aiton forest.'' Dendrochronologia, 79, 126086.</ref><br />
<br />
<ref name="obrien2010">O'Brien, J. J., Kevin Hiers, J., Mitchell, R. J., Varner III, J. M., & Mordecai, K. (2010). ''Acute physiological stress and mortality following fire in a long-unburned longleaf pine ecosystem.'' Fire Ecology, 6(2), 1–12.</ref><br />
<br />
<ref name="dore2012">Dore, S., Montes-Helu, M., Hart, S. C., et al. (2012). ''Recovery of ponderosa pine ecosystem carbon and water fluxes from thinning and stand-replacing fire.'' Global Change Biology, 18(10), 3171–3185.</ref><br />
<br />
<ref name="nolan2014">Nolan, R. H., Lane, P. N., Benyon, R. G., et al. (2014). ''Changes in evapotranspiration following wildfire in resprouting eucalypt forests.'' Ecohydrology, 7(5), 1363–1377.</ref><br />
<br />
<ref name="poon2018">Poon, P. K., & Kinoshita, A. M. (2018). ''Spatial and temporal evapotranspiration trends after wildfire in semi-arid landscapes.'' Journal of Hydrology, 559, 71–83.</ref><br />
<br />
<ref name="cooper2019">Cooper, C. E., Aparecido, L. M., Muir, J. P., et al. (2019). ''Transpiration in recovering mixed loblolly pine and oak stands following wildfire in the Lost Pines region of Texas.'' Ecohydrology, 12(1), e2052.</ref><br />
<br />
<ref name="ma2020">Ma, Q., Bales, R. C., Rungee, J., et al. (2020). ''Wildfire controls on evapotranspiration in California's Sierra Nevada.'' Journal of Hydrology, 590, 125364.</ref><br />
<br />
<ref name="hausler2018">Häusler, M., Nunes, J. P., Soares, P., et al. (2018). ''Assessment of the indirect impact of wildfire (severity) on actual evapotranspiration in eucalyptus forest based on the surface energy balance estimated from remote-sensing techniques.'' International Journal of Remote Sensing, 39(20), 6499–6524.</ref><br />
<br />
<ref name="langford1975">Langford, K. J. (1975). ''Change in yield of water following a bushfire in a forest of Eucalyptus regnans.'' Report No. MMBW-W-0003.</ref><br />
<br />
<ref name="kuczera1987">Kuczera, G. (1987). ''Prediction of water yield reductions following a bushfire in ash-mixed species eucalypt forest.'' Journal of Hydrology, 94(3–4), 215–236.</ref><br />
<br />
<ref name="buckley2012">Buckley, T. N., Turnbull, T. L., Pfautsch, S., et al. (2012). ''Differences in water use between mature and post-fire regrowth stands of subalpine Eucalyptus delegatensis R. Baker.'' Forest Ecology and Management, 270, 1–10.</ref><br />
<br />
<ref name="meili2024">Meili, N., Beringer, J., Zhao, J., & Fatichi, S. (2024). ''Aerodynamic effects cause higher forest evapotranspiration and water yield reductions after wildfires in tall forests.'' Global Change Biology, 30(1), e16995.</ref><br />
<br />
<ref name="wine2016">Wine, M. L., & Cadol, D. (2016). ''Hydrologic effects of large southwestern USA wildfires significantly increase regional water supply: Fact or fiction?'' Environmental Research Letters, 11(8), 085006.</ref><br />
<br />
<ref name="mataix2004">Mataix-Solera, J., & Doerr, S. H. (2004). ''Hydrophobicity and aggregate stability in calcareous topsoils from fire-affected pine forests in southeastern Spain.'' Geoderma, 118(1–2), 77–88.</ref><br />
<br />
<ref name="huffman2001">Huffman, E. L., MacDonald, L. H., & Stednick, J. D. (2001). ''Strength and persistence of fire-induced soil hydrophobicity under ponderosa and lodgepole pine, Colorado Front Range.'' Hydrological Processes, 15(15), 2877–2892.</ref><br />
<br />
<ref name="shakesby2006">Shakesby, R. A., & Doerr, S. H. (2006). ''Wildfire as a hydrological and geomorphological agent.'' Earth-Science Reviews, 74(3–4), 269–307.</ref><br />
<br />
<ref name="williams2022">Williams, A. P., Livneh, B., McKinnon, K. A., Hansen, W. D., Mankin, J. S., Cook, B. I., ... & Lettenmaier, D. P. (2022). ''Growing impact of wildfire on western US water supply.'' Proceedings of the National Academy of Sciences, 119(10), e2114069119.</ref><br />
<br />
<ref name="beeson2001">Beeson, P. C., Martens, S. N., & Breshears, D. D. (2001). ''Simulating overland flow following wildfire: Mapping vulnerability to landscape disturbance.'' Hydrological Processes, 15(15), 2917–2930.</ref><br />
<br />
<ref name="paul2022">Paul, M. J., LeDuc, S. D., Lassiter, M. G., Moorhead, L. C., Noyes, P. D., & Leibowitz, S. G. (2022). ''Wildfire induces changes in receiving waters: A review with considerations for water quality management.'' Water Resources Research, 58(9), e2021WR030699.</ref><br />
<br />
<ref name="smith2011">Smith, H. G., Sheridan, G. J., Lane, P. N., Nyman, P., & Haydon, S. (2011). ''Wildfire effects on water quality in forest catchments: A review with implications for water supply.'' Journal of Hydrology, 396(1–2), 170–192.</ref><br />
<br />
<ref name="hohner2019">Hohner, A. K., Rhoades, C. C., Wilkerson, P., & Rosario-Ortiz, F. L. (2019). ''Wildfires alter forest watersheds and threaten drinking water quality.'' Accounts of Chemical Research, 52(5), 1234–1244.</ref><br />
<br />
<ref name="hohner2017">Hohner, A. K., Terry, L. G., Townsend, E. B., Summers, R. S., & Rosario-Ortiz, F. L. (2017). ''Water treatment process evaluation of wildfire-affected sediment leachates.'' Environmental Science: Water Research & Technology, 3(2), 352–365.</ref><br />
<br />
<ref name="burton2016">Burton, C. A., Hoefen, T. M., Plumlee, G. S., Baumberger, K. L., Backlin, A. R., Gallegos, E., & Fisher, R. N. (2016). ''Trace elements in stormflow, ash, and burned soil following the 2009 Station Fire in Southern California.'' PLOS ONE, 11(5), e0153372.</ref><br />
<br />
<ref name="allen2005">Allen, E. W., Prepas, E. E., Gabos, S., Strachan, W. M., & Zhang, W. (2005). ''Methyl mercury concentrations in macroinvertebrates and fish from burned and undisturbed lakes on the Boreal Plain.'' Canadian Journal of Fisheries and Aquatic Sciences, 62(9), 1963–1977.</ref><br />
<br />
<ref name="kelly2006">Kelly, E. N., Schindler, D. W., St. Louis, V. L., Donald, D. B., & Vladicka, K. E. (2006). ''Forest fire increases mercury accumulation by fishes via food web restructuring and increased mercury inputs.'' Proceedings of the National Academy of Sciences, 103(51), 19380–19385.</ref><br />
<br />
<ref name="emelko2011">Emelko, M. B., Silins, U., Bladon, K. D., & Stone, M. (2011). ''Implications of land disturbance on drinking water treatability in a changing climate: Demonstrating the need for "source water supply and protection" strategies.'' Water Research, 45(2), 461–472.</ref><br />
<br />
<ref name="writer2014">Writer, J. H., Hohner, A., Oropeza, J., Schmidt, A., Cawley, K. M., & Rosario-Ortiz, F. L. (2014). ''Water treatment implications after the High Park wildfire, Colorado.'' Journal ‐ American Water Works Association, 106(4), E189–E199.</ref><br />
<br />
<ref name="earl2003">Earl, S. R., & Blinn, D. W. (2003). ''Effects of wildfire ash on water chemistry and biota in south-western USA streams.'' Freshwater Biology, 48(6), 1015–1030.</ref><br />
<br />
<ref name="rust2019">Rust, A. J., Saxe, S., McCray, J., Rhoades, C. C., & Hogue, T. S. (2019). ''Evaluating the factors responsible for post-fire water quality response in forests of the western USA.'' International Journal of Wildland Fire, 28(10), 769–784.</ref><br />
<br />
</references></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Science_and_applications&diff=4508Science and applications2026-07-09T15:28:40Z<p>JeffreyJLukas: Redirected page to Colorado River Science Wiki#Topics</p>
<hr />
<div>#REDIRECT [[Colorado_River_Science_Wiki#Topics]]<br />
<br />
==Overview==<br />
<br />
This section of the Wiki covers a broad set of topics pertaining to science that is relevant and/or applied to Colorado River management, as well as specific applications of the science, such as streamflow forecasting. <br />
<br />
Each page contains at least the following:<br />
*Summary description of the topic<br />
*The topic's relevance to Colorado River water management<br />
*Annotated links to datasets, tools, and other information resources on that topic<br />
<br />
In the list below, the bolded items are links to active Wiki pages on that topic. The other items are planned future pages.<br />
<br />
We welcome your help in building out the Wiki, by<br />
*Writing up a page on a topic already identified below or a different topic<br />
*Alerting us to new publications, datasets, tools, and other technical resources<br />
*Reviewing existing pages and sending us feedback<br />
<br />
==Topics==<br />
<onlyinclude><br />
<div style="column-count:3;-moz-column-count:3;-webkit-column-count:3"><br />
<br />
'''Cross-cutting reports'''<br />
*'''[[2021 SECURE Water Act reports]]'''<br />
*'''[[2020 CRB State of the Science]]'''<br />
*'''[[2018 CRB Ten Tribes Partnership Tribal Water Study]]''' <br />
*'''[[2012 Colorado River Basin Study]]''' <br />
<br />
'''Weather and climate''' <br />
*'''[[Climate patterns and variability]]''' <br />
*'''[[Recent climate change]]''' <br />
*'''[[Weather and climate monitoring]]''' <br />
*'''[[Weather and climate forecasts]]''' <br />
*'''[[Projected future climate]]'''<br />
*'''[[Colorado River extremes]]''' <br />
<br />
'''Hydrology and water availability''' <br />
*Water balance and basin water budget <br />
*'''[[Snowpack]]''' <br />
*'''[[Soil moisture]]''' <br />
*'''[[Evapotranspiration (ET)]]''' <br />
*Groundwater <br />
*'''[[Streamflow]]''' <br />
*'''[[Paleohydrology]]''' <br />
*Hydrologic variability and trends <br />
*'''[[Seasonal streamflow forecasts]]''' <br />
*Droughts <br />
*'''[[Floods]]''' <br />
*Channel dynamics <br />
*'''[[Hydrologic modeling]]''' <br />
*'''[[Projected future hydrology]]''' <br />
<br />
'''Water operations and planning'''<br />
*'''[[Dams, reservoirs, and other infrastructure]]''' <br />
*Operating guidelines and rules <br />
*'''[[River system models]]''' <br />
**'''[[Colorado River Mid-term Modeling System (CRMMS)]]''' <br />
**'''[[Colorado River Simulation System (CRSS)]]''' <br />
*Planning approaches <br />
<br />
'''Water Use''' <br />
*'''[[Consumptive uses and losses]]''' <br />
**'''[[Agricultural water use]]''' <br />
**'''[[Municipal water use]]''' <br />
**'''[[Reservoir evaporation]]''' <br />
**Channel and bank losses <br />
*Instream flows <br />
*Demand accounting and scenarios <br />
*Future basin demand <br />
<br />
'''Water quality''' <br />
*'''[[Salinity]]''' <br />
*'''[[Metals and acid mine drainage]]'''<br />
*Other contaminants <br />
<br />
'''Geomorphology and sediment''' <br />
*Erosion and sediment sources<br />
*Riverbed sediment dynamics <br />
*Reservoir sedimentation <br />
<br />
'''Ecosystems and environment''' <br />
*Vegetation change <br />
*Wildfires <br />
*Insect infestations and disease <br />
*'''[[Tamarisk and invasive plants]]''' <br />
*'''[[Threatened and endangered fish species]]''' <br />
*'''[[Invasive mussels]]''' <br />
*'''[[Salton Sea]]''' <br />
*'''[[Colorado River Delta]]''' <br />
<br />
'''Societal and economic issues''' <br />
*Benefits of water<br />
*Impacts of shortage and drought <br />
*Social inequity and vulnerability <br />
<br />
</div><br />
</onlyinclude></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Main_Page&diff=4507Main Page2026-07-09T15:26:18Z<p>JeffreyJLukas: Redirected page to Colorado River Science Wiki</p>
<hr />
<div>#REDIRECT [[Colorado_River_Science_Wiki]]<br />
<br />
<br />
[[File:Basin_science_map.png|thumb|400px|'''Figure 1.''' Representation of the different models and data, and their underlying science, applied to decision-making in the Colorado River Basin. (Design: J. Lukas, adapted from L. Payton; basin map by Western Water Assessment (L. Woelders); thumbnail images from University of Washington VIC group, NOAA Colorado Basin River Forecast Center, and Reclamation)]]<br />
<br />
[[File:2025 4 panel Plot Udall.jpg|thumb|400px|link=Current_conditions#The_Colorado_River_.274-panel_plot.27|'''Figure 2.''' The "4-panel plot" showing trends in Colorado River Basin reservoir storage, natural streamflow, precipitation, and temperature, through Water Year 2025. Click on the figure for a larger version. (Figure: Brad Udall; Data: Reclamation - reservoir storage and streamflow; NOAA NCEI - precipitation and temperature)]]<br />
<br />
<br />
<br />
<br />
The '''Colorado River Science Wiki''' is a web-based clearinghouse for scientific and technical information relevant to the Colorado River Basin and the management of its water resources and related natural resources. This clearinghouse is intended to be useful to managers and other decision-makers, to researchers, to the media, and to the broader public. <br />
<br />
We welcome your feedback; please use this [https://docs.google.com/forms/d/e/1FAIpQLSfVXdC1lZde88uk5Nld1qnDDtzXQr1XaDIjFo1KlQ1shCY20A/viewform form] to send us suggestions, or reach us at the contact information below.<br />
<br />
<br />
<br />
[[File:reclamation_logo_blue.webp|300px]]<br />
[[File:logo_spacer.png|30px]]<br />
[[File:AGCI_logo.png|200px]]<br />
[[File:logo_spacer.png|30px]]<br />
[[File:CSU-CWC_logo.png|250px]]<br />
[[File:SWCASC_logo.png|200px]]<br />
[[File:logo_spacer.png|50px]]<br />
[[File:USGS_logo.png|100px]]<br />
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<!-- BEGIN Comment<br />
<br />
[[File:Basin_science_map.png|thumb|400px|'''Figure 1.''' Representation of the different models and data, and their underlying science, applied to decision-making in the Colorado River Basin. (Design: J. Lukas, adapted from L. Payton; basin map by Western Water Assessment (L. Woelders); thumbnail images from University of Washington VIC group, NOAA Colorado Basin River Forecast Center, and Reclamation)]]<br />
<br />
<br />
<[[File:Basin_science_map.png|frame|400px|'''Figure 1.''' Representation of different science applications in the Colorado River Basin. (Basemap source: Western Water Assessment)]]><br />
<br />
<br />
ColoradoRiverScience.Org is being created to provide a clearinghouse about science and data about the Colorado River.<br />
<br />
It is intended for use by Decision Makers, Scientists, Students, the Press, and the Public.<br />
<br />
To obtain a login to allow editing, please contact the site administrator below. <br />
<br />
Edits are subject to review and will not be made public until approved.<br />
<br />
This site is under construction as of 1/21/2020. Currently, a skeleton is in place to allow prototyping and initial design. <br />
<br />
You might find this page to be of use as we build the site. It is a live ongoing compilation of relevant publications.<br />
<br />
Contact Brad Udall Bradley.udall @ colostate.edu for information.<br />
<br />
<br />
Page purpose: Here we show recent scientific, news and policy articles. An archive of older articles will also be accessible as older articles are displaced by newer articles over time.<br />
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{{Toclimit|limit=3}}<br />
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=== Recent Scientific Papers ===<br />
----<br />
==== [https://ametsoc.net/eee/2018/3_Williams0187.pdf Quantifying Human-Induced Temperature Impacts On The 2018 United States Four Corners Hydrologic And Agro-Pastoral Drought ] ====<br />
<br />
Emily Williams <br> <br />
Chris Funk <br> <br />
Shraddhanand Shukla<br> <br />
Daniel McEvoy<br> <br />
<br />
January 23, 2020<br />
<br />
Bulletin of the American Meteorological Society<br />
<br />
===== Summary =====<br />
Human-induced (HI) warming increased Four Corners’ vapor pressure deficits and reduced the Normalized Difference Vegetation Index by ~18%–30%. Without HI warming, March snow water equivalent would have been ~20% higher.<br />
<br />
-----<br />
==== [https://onlinelibrary.wiley.com/doi/full/10.1111/1752-1688.12822?campaign=wolearlyview A Long View of Southern California Water Supply: Perfect Droughts Revisited ]====<br />
[[https://onlinelibrary.wiley.com/doi/full/10.1111/1752-1688.12822?campaign=wolearlyview]]<br />
<br />
C.A. Woodhouse<br />
D.M. Meko<br />
E.R. Bigio<br />
First published: 08 January 2020 <br><br />
Journal of the American Water Resources Association<br />
===== Abstract =====<br />
The impact of drought on water resources in arid and semiarid regions can be buffered by water supplies from different source regions. Simultaneous drought in all major source regions — or perfect drought — poses the most serious challenge to water management. We examine perfect droughts relevant to Southern California (SoCal) water resources with instrumental records and tree‐ring reconstructions for the Sacramento and Colorado Rivers, and SoCal. Perfect droughts have occurred five times since 1906, lasting two to three years, except for the most recent event, 2012–2015. This number and duration of perfect droughts is not unusual in the context of the past six centuries. The modern period stands out for the relatively even distribution of perfect droughts and lacks the clusters of perfect drought documented in prior centuries. In comparison, perfect droughts of the 12th Century were both longer (up to nine years) and more widespread. Perfect droughts of the 20th and 21st Centuries have occurred under different oceanic/atmospheric patterns, zonal and meridional flow, and ENSO or non‐ENSO conditions. Multidecadal coherence across the three regions exists, but it has varied over the past six centuries, resulting in irregular intervals of perfect drought. Although the causes of perfect droughts are not clear, given the long‐term natural variability along with projected changes in climate, it is reasonable to expect more frequent and longer perfect droughts in the future.<br />
<br />
----<br />
==== [https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019GL086689 Bias correction of paleoclimatic reconstructions: A new look at 1200+ years of Upper Colorado River flow] ==== <br />
<br />
<br />
Scott M. Robeson, <br />
Justin T. Maxwell, <br />
Darren L. Ficklin <br><br />
<br />
January 3, 2020 <br><br />
<br />
Geophysical Research Letters<br />
===== Key points =====<br />
# Bias correction makes paleoclimatic models more comparable to observations<br />
# After bias correction, the 1100s Colorado River megadrought became more extreme<br />
# The early 1600s Colorado River pluvial rivals that of the early 20th century after bias correction<br />
<br />
===== Plain Language Summary =====<br />
To study past climates, scientists use indicators such as tree‐ring widths that are related to temperature, precipitation, or streamflow. While these indicators usually are very reliable, they sometimes do not perform as well with extreme events such as intense droughts and wet periods. Here, we adopt a method that can correct for these limitations and apply it to a 1,200+year record of streamflow for the Upper Colorado River, a critical source of water for much of the southwestern United States. After using our method, we find that several extreme events from the tree‐ring record of streamflow were even more intense than formerly thought. In particular, the largest drought in the record that occurred during the 1100s was drier and longer lasting after our correction. During the 56‐year duration of the 1100s drought, our correction makes the flow in the river lower by nearly 52 × 109 m3 of water, which is the equivalent of 1.45 times the capacity of Lake Mead (the largest reservoir in the United States). And, while it was known that the early 1900s was among the wettest periods in the last 1,200+ years, we identify a period in the early 1600s that matches it.<br />
<br />
<br />
<br />
=== Recent News Articles ===<br />
<br />
----<br />
<br />
====[https://phys.org/news/2020-01-climate-hazard-scientists-corners-drought.html Climate hazard scientists connect 2018's Four Corners drought directly to human-caused climate change]====<br />
<br />
January 23, 2020<br />
<br />
----<br />
<br />
[https://coloradosun.com/2020/01/22/climate-change-water-west-computer-model/ We know the earth is warming. We know that will stress water in the West. But we don’t know how.]<br />
<br />
January 22, 2020<br><br />
Mark Jaffe <br><br />
Colorado Sun<br />
<br />
===== Short Summary =====<br />
Two critical, big-picture questions loom: How much snow will fall in the mountains and how much water will there be for the region’s forests, farms and cities.<br />
<br />
------<br />
<br />
====[https://blog.google/products/search/discovering-millions-datasets-web/ Discovering millions of datasets on the web]====<br />
<br />
Natasha Noy<br />
Research Scientist, Google Research<br />
Published Jan 23, 2020<br />
<br />
===== From the First Paragraph =====<br />
<br />
Across the web, there are millions of datasets about nearly any subject that interests you. If you’re looking to buy a puppy, you could find datasets compiling complaints of puppy buyers or studies on puppy cognition. Or if you like skiing, you could find data on revenue of ski resorts or injury rates and participation numbers. Dataset Search has indexed almost 25 million of these datasets, giving you a single place to search for datasets and find links to where the data is. Over the past year, people have tried it out and provided feedback, and now Dataset Search is officially out of beta.<br />
<br />
===== Website =====<br />
[https://datasetsearch.research.google.com Google Dataset Search]<br />
<br />
=== Recent Policy Articles ===<br />
------<br />
<br />
==== Strategies for Managing the Colorado River in an Uncertain Future ====<br />
<br />
[https://qcnr.usu.edu/coloradoriver/files/CCRS_White_Paper_3.pdf Complete White Paper]<br />
[https://qcnr.usu.edu/coloradoriver/files/FS_whitepaper3.pdf Two Page Brief]<br />
<br />
Jian Wang, David E. Rosenberg, Kevin G. Wheeler, John C. Schmidt<br />
February 12, 2020<br />
<br />
'''Understanding What We Don't Know'''<br />
<br />
<br />
Colorado River stakeholders face many uncertainties—issues like climate change, future water demand, and evolving ecological priorities—and are looking for new tools to help cope. Managers and stakeholders need ways to help classify uncertain conditions, manage for them, and create models in the face of a slew of oncoming unknowns.<br />
<br />
<br />
To help Colorado River stakeholders think about, talk about, and better manage the future river, the Center for Colorado River Studies offers a new white paper that distinguishes four levels of decision-making uncertainty. We illustrate each level of uncertainty with examples and show that there is greater uncertainty associated with planning for long time horizons, such as in developing policies that anticipate the increasing possibility of drought, extreme climate events, and unknown patterns of future human use of water. We argue that better public policies will emerge if stakeholders recognize the different levels of uncertainty for future events. <br />
<br />
<br />
Using defined levels of uncertainty can guide stakeholders to appropriate management and modeling tools and lead to more precise and effective conversation and negotiation. <br />
<br />
<br />
'''From the paper: Suggested Practices for an Uncertain Future'''<br />
<br />
#Classify uncertainties by level. <br />
#Include and track more information as it becomes available. <br />
#Define more signposts to signal when future water supply and river ecosystem outcomes deteriorate and trigger an alternative policy. <br />
#Identify more alternative policies for when circumstances trigger a signpost. <br />
#Construct potential pathways that connect signposts and alternative policies over time. <br />
#Match the planning horizon to the uncertainty level. <br />
#Retain more reservoir storage at the end of the model planning horizon to save water for future managers and generations to use. <br />
#Seek better policies that improve water supply and river ecosystem outcomes across more future scenarios, rather than best policies. <br />
#Allow users more flexibility to respond to changing conditions. <br />
#Visualize adaptive policies to show system adaptations over time, identify gaps in policies, and adapt policies to include more information and signposts.<br />
<br />
-----<br />
<br />
==== The Risk of Curtailment under the Colorado River Compact ====<br />
[[https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3483654&download=yes]]<br />
<br />
<br />
Anne Castle <br><br />
John Fleck<br />
<br />
[[https://qcnr.usu.edu/coloradoriver/news/castle_research Summary via Utah State University]]<br />
<br />
=== Other ===<br />
<br />
END COMMENT--!></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Data_and_tools&diff=4506Data and tools2026-07-08T21:14:54Z<p>JeffreyJLukas: </p>
<hr />
<div>==Overview==<br />
<br />
This section of the Colorado River Science Wiki collates all of the ''Data and tools'' items from the pages listed in the [[Colorado_River_Science_Wiki#Topics|Topics]] section of the home page.<br />
<br />
==[[Climate patterns and variability]]==<br />
{{:Climate patterns and variability}}<br />
<br />
==[[Recent climate change]]==<br />
{{:Recent climate change}}<br />
<br />
==[[Weather and climate monitoring]]==<br />
{{:Weather and climate monitoring}}<br />
<br />
==[[Weather and climate forecasts]]==<br />
{{:Weather and climate forecasts}}<br />
<br />
==[[Projected future climate]]==<br />
{{:Projected future climate}}<br />
<br />
==[[Snowpack]]==<br />
{{:Snowpack}} <br />
<br />
==[[Soil moisture]]==<br />
{{:Soil moisture}} <br />
<br />
==[[Evapotranspiration (ET)]]==<br />
{{:Evapotranspiration (ET)}} <br />
<br />
==[[Streamflow]]==<br />
{{:Streamflow}} <br />
<br />
==[[Paleohydrology]]==<br />
{{:Paleohydrology}} <br />
<br />
==[[Seasonal streamflow forecasts]]==<br />
{{:Seasonal streamflow forecasts}}<br />
<br />
==[[Floods]]==<br />
{{:Floods}} <br />
<br />
==[[Hydrologic modeling]]==<br />
{{:Hydrologic modeling}}<br />
<br />
==[[Projected future hydrology]]==<br />
{{:Projected future hydrology}}<br />
<br />
==[[Dams, reservoirs, and other infrastructure]]==<br />
{{:Dams, reservoirs, and other infrastructure}}<br />
<br />
==[[Colorado River Mid-term Modeling System (CRMMS)]]==<br />
{{:Colorado River Mid-term Modeling System (CRMMS)}}<br />
<br />
==[[Colorado River Simulation System (CRSS)]]==<br />
{{:Colorado River Simulation System (CRSS)}}<br />
<br />
==[[Consumptive uses and losses]]==<br />
{{:Consumptive uses and losses}}<br />
<br />
==[[Agricultural water use]]==<br />
{{:Agricultural water use}}<br />
<br />
==[[Municipal water use]]==<br />
{{:Municipal water use}}<br />
<br />
==[[Reservoir evaporation]]==<br />
{{:Reservoir evaporation}}<br />
<br />
==[[Salinity]]==<br />
{{:Salinity}} <br />
<br />
==[[Metals and acid mine drainage]]==<br />
{{:Metals and acid mine drainage}} <br />
<br />
==[[Tamarisk and invasive plants]]==<br />
{{:Tamarisk and invasive plants}} <br />
<br />
==[[Threatened and endangered fish species]]==<br />
{{:Threatened and endangered fish species}} <br />
<br />
==[[Invasive mussels]]==<br />
{{:Invasive mussels}} <br />
<br />
==[[Salton Sea]]==<br />
{{:Salton Sea}} <br />
<br />
==[[Colorado River Delta]]==<br />
{{:Colorado River Delta}}<br />
<br />
<br />
<br />
<br />
<!--<br />
Weather and climate<br />
<br />
Past and current climate <br />
Mechanisms & spatial patterns <br />
Variability & trends over time <br />
Paleoclimate <br />
Recent trends & climate change <br />
Climate monitoring <br />
Weather station networks <br />
Errors and adjustments <br />
Gridded climate products <br />
Drought monitoring <br />
Weather and climate forecasts <br />
Weather forecasts<br />
Subseasonal forecasts<br />
Seasonal forecasts<br />
Decadal climate forecasts <br />
Future climate<br />
Fundamentals of climate change<br />
Climate models <br />
Downscaling<br />
Projected future climate<br />
<br />
Hydrology and water availability<br />
Water balance and basin water budget<br />
Snowpack <br />
Snowpack processes & patterns<br />
Snowpack monitoring<br />
Dust-on-snow <br />
Cloud seeding <br />
Soil moisture <br />
Soil moisture monitoring<br />
Evaporation and evaporative demand<br />
Groundwater <br />
Streamflow<br />
<br />
<br />
Historical (gaged) records<br />
Adjusted streamflow<br />
BoR Natural Flows<br />
Other naturalized<br />
Variability & trends over time <br />
Recent trends & climate change <br />
Real-time streamflows<br />
<br />
Droughts<br />
Dynamics/causes<br />
Impacts<br />
Historic droughts<br />
Paleodroughts <br />
Megadrought <br />
Floods <br />
Historic<br />
Paleofloods<br />
Channel dynamics <br />
Hydrologic modeling <br />
Water operations and planning<br />
Reservoirs and infrastructure <br />
Operating rules<br />
[[River system models]]<br />
<br />
Other models used in the basin<br />
Planning approaches<br />
Future hydrology and water availability<br />
Methods<br />
Future streamflow changes<br />
Other hydrology changes<br />
Synthesis: Future basin water availability <br />
<br />
'''Water Use''' <br />
*Agricultural water use <br />
**ET measurement <br />
**Conservation strategies <br />
*Municipal water use <br />
**Conservation strategies <br />
*Environmental/instream water use <br />
*Other depletions <br />
**Reservoir evaporation <br />
**Channel/bank losses <br />
**Phreatophytic vegetation <br />
*Demand accounting and scenarios <br />
**State/basin reports <br />
**Demand schedules <br />
**Other demand scenarios <br />
*Synthesis: Future basin demand <br />
<br />
'''Water quality and sediment''' <br />
*Salinity <br />
**Salinity monitoring <br />
**Salinity control measures <br />
*Other contaminants <br />
**Uranium mining/tailings <br />
*Sediment <br />
**Erosion/sediment sources <br />
**Reservoir sedimentation <br />
**Riverbed sediment dynamics <br />
<br />
'''Ecosystems and environment''' <br />
*Overview <br />
*Forests <br />
**Disturbances <br />
***Wildfires <br />
***Insect infestations/disease <br />
*Riparian <br />
**Tamarisk and invasive plants <br />
*Aquatic <br />
**T&E fish species <br />
***Upper Basin <br />
***Lower Basin <br />
**Invasive mussels <br />
*Specific hot spots <br />
**Salton Sea <br />
**Colorado River Delta <br />
<br />
'''Societal and economic issues''' <br />
*Benefits of water<br />
*Impacts of shortage and drought <br />
*Social inequity and vulnerability <br />
*Other<br />
--!></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Data_and_tools&diff=4505Data and tools2026-07-08T21:11:41Z<p>JeffreyJLukas: /* Overview */</p>
<hr />
<div>==Overview==<br />
<br />
This section of the Colorado River Science Wiki collates all of the items under the ''Data and tools'' headings from the individual pages listed in the [[Colorado_River_Science_Wiki#Topics|Topics]] section of the home page.<br />
<br />
==[[Climate patterns and variability]]==<br />
{{:Climate patterns and variability}}<br />
<br />
==[[Recent climate change]]==<br />
{{:Recent climate change}}<br />
<br />
==[[Weather and climate monitoring]]==<br />
{{:Weather and climate monitoring}}<br />
<br />
==[[Weather and climate forecasts]]==<br />
{{:Weather and climate forecasts}}<br />
<br />
==[[Projected future climate]]==<br />
{{:Projected future climate}}<br />
<br />
==[[Snowpack]]==<br />
{{:Snowpack}} <br />
<br />
==[[Soil moisture]]==<br />
{{:Soil moisture}} <br />
<br />
==[[Evapotranspiration (ET)]]==<br />
{{:Evapotranspiration (ET)}} <br />
<br />
==[[Streamflow]]==<br />
{{:Streamflow}} <br />
<br />
==[[Paleohydrology]]==<br />
{{:Paleohydrology}} <br />
<br />
==[[Seasonal streamflow forecasts]]==<br />
{{:Seasonal streamflow forecasts}}<br />
<br />
==[[Floods]]==<br />
{{:Floods}} <br />
<br />
==[[Hydrologic modeling]]==<br />
{{:Hydrologic modeling}}<br />
<br />
==[[Projected future hydrology]]==<br />
{{:Projected future hydrology}}<br />
<br />
==[[Dams, reservoirs, and other infrastructure]]==<br />
{{:Dams, reservoirs, and other infrastructure}}<br />
<br />
==[[Colorado River Mid-term Modeling System (CRMMS)]]==<br />
{{:Colorado River Mid-term Modeling System (CRMMS)}}<br />
<br />
==[[Colorado River Simulation System (CRSS)]]==<br />
{{:Colorado River Simulation System (CRSS)}}<br />
<br />
==[[Consumptive uses and losses]]==<br />
{{:Consumptive uses and losses}}<br />
<br />
==[[Agricultural water use]]==<br />
{{:Agricultural water use}}<br />
<br />
==[[Municipal water use]]==<br />
{{:Municipal water use}}<br />
<br />
==[[Reservoir evaporation]]==<br />
{{:Reservoir evaporation}}<br />
<br />
==[[Salinity]]==<br />
{{:Salinity}} <br />
<br />
==[[Metals and acid mine drainage]]==<br />
{{:Metals and acid mine drainage}} <br />
<br />
==[[Tamarisk and invasive plants]]==<br />
{{:Tamarisk and invasive plants}} <br />
<br />
==[[Threatened and endangered fish species]]==<br />
{{:Threatened and endangered fish species}} <br />
<br />
==[[Invasive mussels]]==<br />
{{:Invasive mussels}} <br />
<br />
==[[Salton Sea]]==<br />
{{:Salton Sea}} <br />
<br />
==[[Colorado River Delta]]==<br />
{{:Colorado River Delta}}<br />
<br />
<br />
<br />
<br />
<!--<br />
Weather and climate<br />
<br />
Past and current climate <br />
Mechanisms & spatial patterns <br />
Variability & trends over time <br />
Paleoclimate <br />
Recent trends & climate change <br />
Climate monitoring <br />
Weather station networks <br />
Errors and adjustments <br />
Gridded climate products <br />
Drought monitoring <br />
Weather and climate forecasts <br />
Weather forecasts<br />
Subseasonal forecasts<br />
Seasonal forecasts<br />
Decadal climate forecasts <br />
Future climate<br />
Fundamentals of climate change<br />
Climate models <br />
Downscaling<br />
Projected future climate<br />
<br />
Hydrology and water availability<br />
Water balance and basin water budget<br />
Snowpack <br />
Snowpack processes & patterns<br />
Snowpack monitoring<br />
Dust-on-snow <br />
Cloud seeding <br />
Soil moisture <br />
Soil moisture monitoring<br />
Evaporation and evaporative demand<br />
Groundwater <br />
Streamflow<br />
<br />
<br />
Historical (gaged) records<br />
Adjusted streamflow<br />
BoR Natural Flows<br />
Other naturalized<br />
Variability & trends over time <br />
Recent trends & climate change <br />
Real-time streamflows<br />
<br />
Droughts<br />
Dynamics/causes<br />
Impacts<br />
Historic droughts<br />
Paleodroughts <br />
Megadrought <br />
Floods <br />
Historic<br />
Paleofloods<br />
Channel dynamics <br />
Hydrologic modeling <br />
Water operations and planning<br />
Reservoirs and infrastructure <br />
Operating rules<br />
[[River system models]]<br />
<br />
Other models used in the basin<br />
Planning approaches<br />
Future hydrology and water availability<br />
Methods<br />
Future streamflow changes<br />
Other hydrology changes<br />
Synthesis: Future basin water availability <br />
<br />
'''Water Use''' <br />
*Agricultural water use <br />
**ET measurement <br />
**Conservation strategies <br />
*Municipal water use <br />
**Conservation strategies <br />
*Environmental/instream water use <br />
*Other depletions <br />
**Reservoir evaporation <br />
**Channel/bank losses <br />
**Phreatophytic vegetation <br />
*Demand accounting and scenarios <br />
**State/basin reports <br />
**Demand schedules <br />
**Other demand scenarios <br />
*Synthesis: Future basin demand <br />
<br />
'''Water quality and sediment''' <br />
*Salinity <br />
**Salinity monitoring <br />
**Salinity control measures <br />
*Other contaminants <br />
**Uranium mining/tailings <br />
*Sediment <br />
**Erosion/sediment sources <br />
**Reservoir sedimentation <br />
**Riverbed sediment dynamics <br />
<br />
'''Ecosystems and environment''' <br />
*Overview <br />
*Forests <br />
**Disturbances <br />
***Wildfires <br />
***Insect infestations/disease <br />
*Riparian <br />
**Tamarisk and invasive plants <br />
*Aquatic <br />
**T&E fish species <br />
***Upper Basin <br />
***Lower Basin <br />
**Invasive mussels <br />
*Specific hot spots <br />
**Salton Sea <br />
**Colorado River Delta <br />
<br />
'''Societal and economic issues''' <br />
*Benefits of water<br />
*Impacts of shortage and drought <br />
*Social inequity and vulnerability <br />
*Other<br />
--!></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Data_and_tools&diff=4504Data and tools2026-07-08T21:10:49Z<p>JeffreyJLukas: /* Overview */</p>
<hr />
<div>==Overview==<br />
<br />
This section of the Colorado River Science Wiki collates all of the items under the ''Data and tools'' headings on the pages in the [[Colorado_River_Science_Wiki#Topics|Topics]] section of the home page.<br />
<br />
==[[Climate patterns and variability]]==<br />
{{:Climate patterns and variability}}<br />
<br />
==[[Recent climate change]]==<br />
{{:Recent climate change}}<br />
<br />
==[[Weather and climate monitoring]]==<br />
{{:Weather and climate monitoring}}<br />
<br />
==[[Weather and climate forecasts]]==<br />
{{:Weather and climate forecasts}}<br />
<br />
==[[Projected future climate]]==<br />
{{:Projected future climate}}<br />
<br />
==[[Snowpack]]==<br />
{{:Snowpack}} <br />
<br />
==[[Soil moisture]]==<br />
{{:Soil moisture}} <br />
<br />
==[[Evapotranspiration (ET)]]==<br />
{{:Evapotranspiration (ET)}} <br />
<br />
==[[Streamflow]]==<br />
{{:Streamflow}} <br />
<br />
==[[Paleohydrology]]==<br />
{{:Paleohydrology}} <br />
<br />
==[[Seasonal streamflow forecasts]]==<br />
{{:Seasonal streamflow forecasts}}<br />
<br />
==[[Floods]]==<br />
{{:Floods}} <br />
<br />
==[[Hydrologic modeling]]==<br />
{{:Hydrologic modeling}}<br />
<br />
==[[Projected future hydrology]]==<br />
{{:Projected future hydrology}}<br />
<br />
==[[Dams, reservoirs, and other infrastructure]]==<br />
{{:Dams, reservoirs, and other infrastructure}}<br />
<br />
==[[Colorado River Mid-term Modeling System (CRMMS)]]==<br />
{{:Colorado River Mid-term Modeling System (CRMMS)}}<br />
<br />
==[[Colorado River Simulation System (CRSS)]]==<br />
{{:Colorado River Simulation System (CRSS)}}<br />
<br />
==[[Consumptive uses and losses]]==<br />
{{:Consumptive uses and losses}}<br />
<br />
==[[Agricultural water use]]==<br />
{{:Agricultural water use}}<br />
<br />
==[[Municipal water use]]==<br />
{{:Municipal water use}}<br />
<br />
==[[Reservoir evaporation]]==<br />
{{:Reservoir evaporation}}<br />
<br />
==[[Salinity]]==<br />
{{:Salinity}} <br />
<br />
==[[Metals and acid mine drainage]]==<br />
{{:Metals and acid mine drainage}} <br />
<br />
==[[Tamarisk and invasive plants]]==<br />
{{:Tamarisk and invasive plants}} <br />
<br />
==[[Threatened and endangered fish species]]==<br />
{{:Threatened and endangered fish species}} <br />
<br />
==[[Invasive mussels]]==<br />
{{:Invasive mussels}} <br />
<br />
==[[Salton Sea]]==<br />
{{:Salton Sea}} <br />
<br />
==[[Colorado River Delta]]==<br />
{{:Colorado River Delta}}<br />
<br />
<br />
<br />
<br />
<!--<br />
Weather and climate<br />
<br />
Past and current climate <br />
Mechanisms & spatial patterns <br />
Variability & trends over time <br />
Paleoclimate <br />
Recent trends & climate change <br />
Climate monitoring <br />
Weather station networks <br />
Errors and adjustments <br />
Gridded climate products <br />
Drought monitoring <br />
Weather and climate forecasts <br />
Weather forecasts<br />
Subseasonal forecasts<br />
Seasonal forecasts<br />
Decadal climate forecasts <br />
Future climate<br />
Fundamentals of climate change<br />
Climate models <br />
Downscaling<br />
Projected future climate<br />
<br />
Hydrology and water availability<br />
Water balance and basin water budget<br />
Snowpack <br />
Snowpack processes & patterns<br />
Snowpack monitoring<br />
Dust-on-snow <br />
Cloud seeding <br />
Soil moisture <br />
Soil moisture monitoring<br />
Evaporation and evaporative demand<br />
Groundwater <br />
Streamflow<br />
<br />
<br />
Historical (gaged) records<br />
Adjusted streamflow<br />
BoR Natural Flows<br />
Other naturalized<br />
Variability & trends over time <br />
Recent trends & climate change <br />
Real-time streamflows<br />
<br />
Droughts<br />
Dynamics/causes<br />
Impacts<br />
Historic droughts<br />
Paleodroughts <br />
Megadrought <br />
Floods <br />
Historic<br />
Paleofloods<br />
Channel dynamics <br />
Hydrologic modeling <br />
Water operations and planning<br />
Reservoirs and infrastructure <br />
Operating rules<br />
[[River system models]]<br />
<br />
Other models used in the basin<br />
Planning approaches<br />
Future hydrology and water availability<br />
Methods<br />
Future streamflow changes<br />
Other hydrology changes<br />
Synthesis: Future basin water availability <br />
<br />
'''Water Use''' <br />
*Agricultural water use <br />
**ET measurement <br />
**Conservation strategies <br />
*Municipal water use <br />
**Conservation strategies <br />
*Environmental/instream water use <br />
*Other depletions <br />
**Reservoir evaporation <br />
**Channel/bank losses <br />
**Phreatophytic vegetation <br />
*Demand accounting and scenarios <br />
**State/basin reports <br />
**Demand schedules <br />
**Other demand scenarios <br />
*Synthesis: Future basin demand <br />
<br />
'''Water quality and sediment''' <br />
*Salinity <br />
**Salinity monitoring <br />
**Salinity control measures <br />
*Other contaminants <br />
**Uranium mining/tailings <br />
*Sediment <br />
**Erosion/sediment sources <br />
**Reservoir sedimentation <br />
**Riverbed sediment dynamics <br />
<br />
'''Ecosystems and environment''' <br />
*Overview <br />
*Forests <br />
**Disturbances <br />
***Wildfires <br />
***Insect infestations/disease <br />
*Riparian <br />
**Tamarisk and invasive plants <br />
*Aquatic <br />
**T&E fish species <br />
***Upper Basin <br />
***Lower Basin <br />
**Invasive mussels <br />
*Specific hot spots <br />
**Salton Sea <br />
**Colorado River Delta <br />
<br />
'''Societal and economic issues''' <br />
*Benefits of water<br />
*Impacts of shortage and drought <br />
*Social inequity and vulnerability <br />
*Other<br />
--!></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Data_and_tools&diff=4503Data and tools2026-07-08T21:10:23Z<p>JeffreyJLukas: /* Overview */</p>
<hr />
<div>==Overview==<br />
<br />
This section of the Colorado River Science Wiki collates all of the items under the ''Data and tools'' headings on the pages in the [[Colorado_River_Science_Wiki#Topics|Topics]] section, and lists those datasets and tools below in the same order as the the pages in the [[Science and applications]] section.<br />
<br />
==[[Climate patterns and variability]]==<br />
{{:Climate patterns and variability}}<br />
<br />
==[[Recent climate change]]==<br />
{{:Recent climate change}}<br />
<br />
==[[Weather and climate monitoring]]==<br />
{{:Weather and climate monitoring}}<br />
<br />
==[[Weather and climate forecasts]]==<br />
{{:Weather and climate forecasts}}<br />
<br />
==[[Projected future climate]]==<br />
{{:Projected future climate}}<br />
<br />
==[[Snowpack]]==<br />
{{:Snowpack}} <br />
<br />
==[[Soil moisture]]==<br />
{{:Soil moisture}} <br />
<br />
==[[Evapotranspiration (ET)]]==<br />
{{:Evapotranspiration (ET)}} <br />
<br />
==[[Streamflow]]==<br />
{{:Streamflow}} <br />
<br />
==[[Paleohydrology]]==<br />
{{:Paleohydrology}} <br />
<br />
==[[Seasonal streamflow forecasts]]==<br />
{{:Seasonal streamflow forecasts}}<br />
<br />
==[[Floods]]==<br />
{{:Floods}} <br />
<br />
==[[Hydrologic modeling]]==<br />
{{:Hydrologic modeling}}<br />
<br />
==[[Projected future hydrology]]==<br />
{{:Projected future hydrology}}<br />
<br />
==[[Dams, reservoirs, and other infrastructure]]==<br />
{{:Dams, reservoirs, and other infrastructure}}<br />
<br />
==[[Colorado River Mid-term Modeling System (CRMMS)]]==<br />
{{:Colorado River Mid-term Modeling System (CRMMS)}}<br />
<br />
==[[Colorado River Simulation System (CRSS)]]==<br />
{{:Colorado River Simulation System (CRSS)}}<br />
<br />
==[[Consumptive uses and losses]]==<br />
{{:Consumptive uses and losses}}<br />
<br />
==[[Agricultural water use]]==<br />
{{:Agricultural water use}}<br />
<br />
==[[Municipal water use]]==<br />
{{:Municipal water use}}<br />
<br />
==[[Reservoir evaporation]]==<br />
{{:Reservoir evaporation}}<br />
<br />
==[[Salinity]]==<br />
{{:Salinity}} <br />
<br />
==[[Metals and acid mine drainage]]==<br />
{{:Metals and acid mine drainage}} <br />
<br />
==[[Tamarisk and invasive plants]]==<br />
{{:Tamarisk and invasive plants}} <br />
<br />
==[[Threatened and endangered fish species]]==<br />
{{:Threatened and endangered fish species}} <br />
<br />
==[[Invasive mussels]]==<br />
{{:Invasive mussels}} <br />
<br />
==[[Salton Sea]]==<br />
{{:Salton Sea}} <br />
<br />
==[[Colorado River Delta]]==<br />
{{:Colorado River Delta}}<br />
<br />
<br />
<br />
<br />
<!--<br />
Weather and climate<br />
<br />
Past and current climate <br />
Mechanisms & spatial patterns <br />
Variability & trends over time <br />
Paleoclimate <br />
Recent trends & climate change <br />
Climate monitoring <br />
Weather station networks <br />
Errors and adjustments <br />
Gridded climate products <br />
Drought monitoring <br />
Weather and climate forecasts <br />
Weather forecasts<br />
Subseasonal forecasts<br />
Seasonal forecasts<br />
Decadal climate forecasts <br />
Future climate<br />
Fundamentals of climate change<br />
Climate models <br />
Downscaling<br />
Projected future climate<br />
<br />
Hydrology and water availability<br />
Water balance and basin water budget<br />
Snowpack <br />
Snowpack processes & patterns<br />
Snowpack monitoring<br />
Dust-on-snow <br />
Cloud seeding <br />
Soil moisture <br />
Soil moisture monitoring<br />
Evaporation and evaporative demand<br />
Groundwater <br />
Streamflow<br />
<br />
<br />
Historical (gaged) records<br />
Adjusted streamflow<br />
BoR Natural Flows<br />
Other naturalized<br />
Variability & trends over time <br />
Recent trends & climate change <br />
Real-time streamflows<br />
<br />
Droughts<br />
Dynamics/causes<br />
Impacts<br />
Historic droughts<br />
Paleodroughts <br />
Megadrought <br />
Floods <br />
Historic<br />
Paleofloods<br />
Channel dynamics <br />
Hydrologic modeling <br />
Water operations and planning<br />
Reservoirs and infrastructure <br />
Operating rules<br />
[[River system models]]<br />
<br />
Other models used in the basin<br />
Planning approaches<br />
Future hydrology and water availability<br />
Methods<br />
Future streamflow changes<br />
Other hydrology changes<br />
Synthesis: Future basin water availability <br />
<br />
'''Water Use''' <br />
*Agricultural water use <br />
**ET measurement <br />
**Conservation strategies <br />
*Municipal water use <br />
**Conservation strategies <br />
*Environmental/instream water use <br />
*Other depletions <br />
**Reservoir evaporation <br />
**Channel/bank losses <br />
**Phreatophytic vegetation <br />
*Demand accounting and scenarios <br />
**State/basin reports <br />
**Demand schedules <br />
**Other demand scenarios <br />
*Synthesis: Future basin demand <br />
<br />
'''Water quality and sediment''' <br />
*Salinity <br />
**Salinity monitoring <br />
**Salinity control measures <br />
*Other contaminants <br />
**Uranium mining/tailings <br />
*Sediment <br />
**Erosion/sediment sources <br />
**Reservoir sedimentation <br />
**Riverbed sediment dynamics <br />
<br />
'''Ecosystems and environment''' <br />
*Overview <br />
*Forests <br />
**Disturbances <br />
***Wildfires <br />
***Insect infestations/disease <br />
*Riparian <br />
**Tamarisk and invasive plants <br />
*Aquatic <br />
**T&E fish species <br />
***Upper Basin <br />
***Lower Basin <br />
**Invasive mussels <br />
*Specific hot spots <br />
**Salton Sea <br />
**Colorado River Delta <br />
<br />
'''Societal and economic issues''' <br />
*Benefits of water<br />
*Impacts of shortage and drought <br />
*Social inequity and vulnerability <br />
*Other<br />
--!></div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Colorado_River_Science_Wiki&diff=4502Colorado River Science Wiki2026-07-08T21:07:40Z<p>JeffreyJLukas: /* Topic pages */</p>
<hr />
<div>[[File:WikiBanner3.png|none|900px|']]<br />
<br />
Welcome to the '''Colorado River Science Wiki''', a web-based clearinghouse for scientific and technical information relevant to the Colorado River Basin and the management of its water resources and related natural resources. We welcome your feedback; please use this [https://docs.google.com/forms/d/e/1FAIpQLSfVXdC1lZde88uk5Nld1qnDDtzXQr1XaDIjFo1KlQ1shCY20A/viewform form] to send us suggestions, or reach us at the contact information on [[About this wiki]].<br />
<br />
<div style="column-count:2;-moz-column-count:2;-webkit-column-count:2"><br />
==Resources==<br />
*'''[[Data and tools]]'''<br />
*'''[[Who's who]]'''<br />
*'''[[Current conditions]]''' <br />
*'''[[About the river]]''' <br />
*'''[[Events|Events calendar]]'''<br />
<br />
==Publications==<br />
*'''[[New research]]''' (since 2020)<br />
*'''[https://www.zotero.org/groups/4274378/colorado_river_science_wiki/library Searchable database (Zotero library)]'''<br />
**'''[[2021 SECURE Water Act reports]]'''<br />
**'''[[2020 CRB State of the Science]]'''<br />
**'''[[2018 CRB Ten Tribes Partnership Tribal Water Study|2018 CRB Tribal Water Study]]''' <br />
**'''[[2012 Colorado River Basin Study]]'''<br />
<br />
</div><br />
<br />
==Topics==<br />
<div style="column-count:3;-moz-column-count:3;-webkit-column-count:3"><br />
<br />
'''Weather and climate''' <br />
*'''[[Climate patterns and variability]]''' <br />
*'''[[Recent climate change]]''' <br />
*'''[[Weather and climate monitoring]]''' <br />
*'''[[Weather and climate forecasts]]''' <br />
*'''[[Projected future climate]]'''<br />
*'''[[Colorado River extremes]]''' <br />
<br />
'''Hydrology and water availability''' <br />
*'''[[Snowpack]]''' <br />
*'''[[Soil moisture]]''' <br />
*'''[[Evapotranspiration (ET)]]''' <br />
*'''[[Streamflow]]''' <br />
*'''[[Paleohydrology]]''' <br />
*'''[[Seasonal streamflow forecasts]]''' <br />
*'''[[Floods]]''' <br />
*'''[[Hydrologic modeling]]''' <br />
*'''[[Projected future hydrology]]''' <br />
<br />
'''Water operations and planning'''<br />
*'''[[Dams, reservoirs, and other infrastructure]]''' <br />
*'''[[River system models]]''' <br />
**'''[[Colorado River Mid-term Modeling System (CRMMS)]]''' <br />
**'''[[Colorado River Simulation System (CRSS)]]''' <br />
<br />
'''Water Use''' <br />
*'''[[Consumptive uses and losses]]''' <br />
**'''[[Agricultural water use]]''' <br />
**'''[[Municipal water use]]''' <br />
**'''[[Reservoir evaporation]]''' <br />
<br />
'''Water quality''' <br />
*'''[[Salinity]]''' <br />
*'''[[Metals and acid mine drainage]]'''<br />
<br />
'''Ecosystems and environment''' <br />
*'''[[Tamarisk and invasive plants]]''' <br />
*'''[[Threatened and endangered fish species]]''' <br />
*'''[[Invasive mussels]]''' <br />
*'''[[Salton Sea]]''' <br />
*'''[[Colorado River Delta]]''' <br />
<br />
'''Societal context'''<br />
*'''[[Water law and policy]]''' <br />
<br />
</div><br />
<br />
<br />
<br />
<br />
<br />
[[File:reclamation_logo_blue.webp|300px]]<br />
[[File:logo_spacer.png|30px]]<br />
[[File:AGCI_logo.png|200px]]<br />
[[File:logo_spacer.png|30px]]<br />
[[File:CSU-CWC_logo.png|250px]]<br />
[[File:SWCASC_logo.png|200px]]<br />
[[File:logo_spacer.png|50px]]<br />
[[File:USGS_logo.png|100px]]</div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=About_this_wiki&diff=4501About this wiki2026-07-08T20:44:02Z<p>JeffreyJLukas: </p>
<hr />
<div>The '''Colorado River Science Wiki''' is a web-based clearinghouse for scientific and technical information relevant to the Colorado River Basin and the management of its water resources and related natural resources. This wiki is intended to be useful to managers and other decision-makers, researchers, students, media, and the broader interested public. The objectives for the Wiki: <br />
<br />
*Share recent and ongoing Colorado River research efforts and findings<br />
*Provide up-to-date synthesis of the science relevant to management<br />
*Allow one-stop access to key technical datasets and data tools<br />
*Help inform discussions about the next [https://www.usbr.gov/ColoradoRiverBasin/ Interim Guidelines] <br />
*Engage the greater Colorado River community in a joint information-gathering effort <br />
<br />
We welcome your feedback; please use this [https://docs.google.com/forms/d/e/1FAIpQLSfVXdC1lZde88uk5Nld1qnDDtzXQr1XaDIjFo1KlQ1shCY20A/viewform form] to send us suggestions, or reach us at the contact information below.<br />
<br />
==Outline==<br />
<br />
There are six main sections in the Wiki. Each section can be accessed via the navigation panel on the left side of the page. <br />
<br />
'''''[[Science and applications]]''''' <br />
<br />
Provides up-to-date information across dozens of areas of management-relevant science. Each page has at least the following:<br />
*Summary description of the topic<br />
*The topic's relevance to Colorado River water management<br />
*Annotated links to datasets, tools, and other information and science synthesis on that topic<br />
<br />
'''''[[Data and tools]]''''' <br />
<br />
Collates all of the annotated links to the datasets and tools from Section 1, to make them available in one place. <br />
<br />
'''''[[New research]]''''' <br />
<br />
Lists, by year and by subject, research studies and relevant reports published since 2020.<br />
<br />
'''''[[Water law and policy]]''''' <br />
<br />
Describes the legal and policy context in which the science and applications to inform water management are implemented. <br />
<br />
'''''[[Who's who]]''''' <br />
<br />
Identifies key players in the science-to-applications (aka research-to-operations, or R2O) chain in the basin, and provides links to homepages and other resources. <br />
<br />
'''''[[About the river]]''''' <br />
<br />
Provides a very brief introduction to the Colorado River and the challenges that have emerged in the 21st century.<br />
<br />
==Use of AI==<br />
<br />
All content on the Colorado River Science Wiki is written without the use of generative AI tools. We do use AI-assisted tools, such as the Semantic Scholar and Google Scholar search tools, to find [[new research]] publications.<br />
<br />
==Contact== <br />
<br />
The development of the Wiki is being carried out by Julie Vano and Tanya Petach (Aspen Global Change Institute), Brad Udall (Colorado Water Center, Colorado State University), and Jeff Lukas (Lukas Climate Research and Consulting). <br />
<br />
To provide feedback on the Wiki content, please see the [[Feedback]] page.<br />
<br />
For other questions about the Wiki, please contact Julie (jvano [at] agci.org) or Brad (Bradley.udall [at] colostate.edu).<br />
<br />
==Acknowledgements==<br />
<br />
The development of the Wiki is currently supported by funding from the Bureau of Reclamation’s Upper Colorado River Basin (Interior Region 7) and Lower Colorado Basin (Interior Region 8), as well as in-kind support from Aspen Global Change Institute and the Colorado State University Colorado Water Center. <br />
<br />
We are seeking additional funding for the Wiki from the Colorado River community; please contact Julie (jvano [at] agci.org) if you are interested in supporting this effort. <br />
<br />
From 2020 to 2024, the development of the Wiki was also supported by U.S. Geological Survey Southwest Climate Adaptation Science Center (SW CASC) Grant #G18AC00320, and funding and in-kind support from the Colorado State University Colorado Water Center.</div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Colorado_River_Science_Wiki&diff=4500Colorado River Science Wiki2026-07-08T20:41:57Z<p>JeffreyJLukas: </p>
<hr />
<div>[[File:WikiBanner3.png|none|900px|']]<br />
<br />
Welcome to the '''Colorado River Science Wiki''', a web-based clearinghouse for scientific and technical information relevant to the Colorado River Basin and the management of its water resources and related natural resources. We welcome your feedback; please use this [https://docs.google.com/forms/d/e/1FAIpQLSfVXdC1lZde88uk5Nld1qnDDtzXQr1XaDIjFo1KlQ1shCY20A/viewform form] to send us suggestions, or reach us at the contact information on [[About this wiki]].<br />
<br />
<div style="column-count:2;-moz-column-count:2;-webkit-column-count:2"><br />
==Resources==<br />
*'''[[Data and tools]]'''<br />
*'''[[Who's who]]'''<br />
*'''[[Current conditions]]''' <br />
*'''[[About the river]]''' <br />
*'''[[Events|Events calendar]]'''<br />
<br />
==Publications==<br />
*'''[[New research]]''' (since 2020)<br />
*'''[https://www.zotero.org/groups/4274378/colorado_river_science_wiki/library Searchable database (Zotero library)]'''<br />
**'''[[2021 SECURE Water Act reports]]'''<br />
**'''[[2020 CRB State of the Science]]'''<br />
**'''[[2018 CRB Ten Tribes Partnership Tribal Water Study|2018 CRB Tribal Water Study]]''' <br />
**'''[[2012 Colorado River Basin Study]]'''<br />
<br />
</div><br />
<br />
==Topic pages==<br />
<div style="column-count:3;-moz-column-count:3;-webkit-column-count:3"><br />
<br />
'''Weather and climate''' <br />
*'''[[Climate patterns and variability]]''' <br />
*'''[[Recent climate change]]''' <br />
*'''[[Weather and climate monitoring]]''' <br />
*'''[[Weather and climate forecasts]]''' <br />
*'''[[Projected future climate]]'''<br />
*'''[[Colorado River extremes]]''' <br />
<br />
'''Hydrology and water availability''' <br />
*'''[[Snowpack]]''' <br />
*'''[[Soil moisture]]''' <br />
*'''[[Evapotranspiration (ET)]]''' <br />
*'''[[Streamflow]]''' <br />
*'''[[Paleohydrology]]''' <br />
*'''[[Seasonal streamflow forecasts]]''' <br />
*'''[[Floods]]''' <br />
*'''[[Hydrologic modeling]]''' <br />
*'''[[Projected future hydrology]]''' <br />
<br />
'''Water operations and planning'''<br />
*'''[[Dams, reservoirs, and other infrastructure]]''' <br />
*'''[[River system models]]''' <br />
**'''[[Colorado River Mid-term Modeling System (CRMMS)]]''' <br />
**'''[[Colorado River Simulation System (CRSS)]]''' <br />
<br />
'''Water Use''' <br />
*'''[[Consumptive uses and losses]]''' <br />
**'''[[Agricultural water use]]''' <br />
**'''[[Municipal water use]]''' <br />
**'''[[Reservoir evaporation]]''' <br />
<br />
'''Water quality''' <br />
*'''[[Salinity]]''' <br />
*'''[[Metals and acid mine drainage]]'''<br />
<br />
'''Ecosystems and environment''' <br />
*'''[[Tamarisk and invasive plants]]''' <br />
*'''[[Threatened and endangered fish species]]''' <br />
*'''[[Invasive mussels]]''' <br />
*'''[[Salton Sea]]''' <br />
*'''[[Colorado River Delta]]''' <br />
<br />
'''Societal context'''<br />
*'''[[Water law and policy]]''' <br />
<br />
</div><br />
<br />
<br />
<br />
<br />
<br />
[[File:reclamation_logo_blue.webp|300px]]<br />
[[File:logo_spacer.png|30px]]<br />
[[File:AGCI_logo.png|200px]]<br />
[[File:logo_spacer.png|30px]]<br />
[[File:CSU-CWC_logo.png|250px]]<br />
[[File:SWCASC_logo.png|200px]]<br />
[[File:logo_spacer.png|50px]]<br />
[[File:USGS_logo.png|100px]]</div>JeffreyJLukashttp://coloradoriverscience.org/index.php?title=Colorado_River_Science_Wiki&diff=4499Colorado River Science Wiki2026-07-08T20:40:33Z<p>JeffreyJLukas: /* Publications */</p>
<hr />
<div>[[File:WikiBanner3.png|none|900px|']]<br />
<br />
Welcome to the '''Colorado River Science Wiki''', a web-based clearinghouse for scientific and technical information relevant to the Colorado River Basin and the management of its water resources and related natural resources. This wiki is intended to be useful to resource managers and other decision-makers, researchers, students, the media, and the broader public. <br />
<br />
<div style="column-count:2;-moz-column-count:2;-webkit-column-count:2"><br />
==Resources==<br />
*'''[[Data and tools]]'''<br />
*'''[[Who's who]]'''<br />
*'''[[Current conditions]]''' <br />
*'''[[About the river]]''' <br />
*'''[[Events|Events calendar]]'''<br />
<br />
==Publications==<br />
*'''[[New research]]''' (since 2020)<br />
*'''[https://www.zotero.org/groups/4274378/colorado_river_science_wiki/library Searchable database (Zotero library)]'''<br />
**'''[[2021 SECURE Water Act reports]]'''<br />
**'''[[2020 CRB State of the Science]]'''<br />
**'''[[2018 CRB Ten Tribes Partnership Tribal Water Study|2018 CRB Tribal Water Study]]''' <br />
**'''[[2012 Colorado River Basin Study]]'''<br />
<br />
</div><br />
<br />
==Topic pages==<br />
<div style="column-count:3;-moz-column-count:3;-webkit-column-count:3"><br />
<br />
'''Weather and climate''' <br />
*'''[[Climate patterns and variability]]''' <br />
*'''[[Recent climate change]]''' <br />
*'''[[Weather and climate monitoring]]''' <br />
*'''[[Weather and climate forecasts]]''' <br />
*'''[[Projected future climate]]'''<br />
*'''[[Colorado River extremes]]''' <br />
<br />
'''Hydrology and water availability''' <br />
*'''[[Snowpack]]''' <br />
*'''[[Soil moisture]]''' <br />
*'''[[Evapotranspiration (ET)]]''' <br />
*'''[[Streamflow]]''' <br />
*'''[[Paleohydrology]]''' <br />
*'''[[Seasonal streamflow forecasts]]''' <br />
*'''[[Floods]]''' <br />
*'''[[Hydrologic modeling]]''' <br />
*'''[[Projected future hydrology]]''' <br />
<br />
'''Water operations and planning'''<br />
*'''[[Dams, reservoirs, and other infrastructure]]''' <br />
*'''[[River system models]]''' <br />
**'''[[Colorado River Mid-term Modeling System (CRMMS)]]''' <br />
**'''[[Colorado River Simulation System (CRSS)]]''' <br />
<br />
'''Water Use''' <br />
*'''[[Consumptive uses and losses]]''' <br />
**'''[[Agricultural water use]]''' <br />
**'''[[Municipal water use]]''' <br />
**'''[[Reservoir evaporation]]''' <br />
<br />
'''Water quality''' <br />
*'''[[Salinity]]''' <br />
*'''[[Metals and acid mine drainage]]'''<br />
<br />
'''Ecosystems and environment''' <br />
*'''[[Tamarisk and invasive plants]]''' <br />
*'''[[Threatened and endangered fish species]]''' <br />
*'''[[Invasive mussels]]''' <br />
*'''[[Salton Sea]]''' <br />
*'''[[Colorado River Delta]]''' <br />
<br />
'''Societal context'''<br />
*'''[[Water law and policy]]''' <br />
<br />
</div><br />
<br />
<br />
We welcome your feedback; please use this [https://docs.google.com/forms/d/e/1FAIpQLSfVXdC1lZde88uk5Nld1qnDDtzXQr1XaDIjFo1KlQ1shCY20A/viewform form] to send us suggestions, or reach us at the contact information on [[About this wiki]].<br />
<br />
<br />
[[File:reclamation_logo_blue.webp|300px]]<br />
[[File:logo_spacer.png|30px]]<br />
[[File:AGCI_logo.png|200px]]<br />
[[File:logo_spacer.png|30px]]<br />
[[File:CSU-CWC_logo.png|250px]]<br />
[[File:SWCASC_logo.png|200px]]<br />
[[File:logo_spacer.png|50px]]<br />
[[File:USGS_logo.png|100px]]</div>JeffreyJLukas