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Wildfire and water

TanyaPetach — Fri, 24 Jul 2026 00:24:19 GMT

Wildfire and water

JeffreyJLukas — Thu, 23 Jul 2026 19:43:25 GMT

Overview

← Older revision		Revision as of 15:43, 23 July 2026
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	[[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)]]		[[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)]]

	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" />		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" />
	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" />		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" />

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	===Land management to reduce fire risk and impacts===		===Land management to reduce fire risk and impacts===

	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.		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.

	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.		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" />

	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.		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.

	==Data and ~~Tools~~==		==Data and tools==

	<onlyinclude>		<onlyinclude>
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	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).		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).
	</onlyinclude>		</onlyinclude>
	==Additional ~~Resources~~==
			==Additional resources==

	===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===		===[https://iopscience.iop.org/article/10.1088/3033-4942/ae2a64/meta A review of post-wildfire shifts in streamflow]===

	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.		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.

	==Notes==		==Notes==
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	<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>		<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>

			<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>

			<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>

			<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>

			<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>

			<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>

			<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>


	</references>		</references>

MediaWiki:Sidebar

JeffreyJLukas — Thu, 23 Jul 2026 15:14:50 GMT

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	* Key Items		* Key Items
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Wildfire and water

JeffreyJLukas — Thu, 23 Jul 2026 15:01:57 GMT

← Older revision		Revision as of 11:01, 23 July 2026
(One intermediate revision by the same user not shown)
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	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" />		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" />
	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" />		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" />

	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.		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.
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	<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>		<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>

	<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>

	<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>		<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>

	<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>

	<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>		<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>
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	<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>		<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>

	~~<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>~~

	<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>

	<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>		<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>
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	<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>		<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>

	~~<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>~~

	<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>		<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>

	<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>

	<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>		<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>
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	<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>		<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>

	<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>

	<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>		<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>

	<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>		<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>

	<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>

	<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>		<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>

Wildfire and water

TanyaPetach — Mon, 20 Jul 2026 20:39:06 GMT

Wildfire and water

JeffreyJLukas — Thu, 16 Jul 2026 22:18:12 GMT

Show changes

Wildfire and water

TanyaPetach — Mon, 13 Jul 2026 17:32:35 GMT

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 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.
 ==Notes==

← Older revision		Revision as of 16:39, 20 July 2026
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	[[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)]]		[[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)]]

	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" />		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" />
	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" />		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" />

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	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.		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.

	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" />		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" />

	====Soil infiltration and runoff====		====Soil infiltration and runoff====

	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" />		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" />

	===Water quality impacts===		===Water quality impacts===
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	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" />		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" />

	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" />		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" />

	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" />		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" />

	===Land management to reduce fire risk and impacts===		===Land management to reduce fire risk and impacts===