Projected future hydrology - Revision history

JeffreyJLukas: /* Overview */

2024-10-23T20:23:32Z

Overview

← Older revision		Revision as of 16:23, 23 October 2024
Line 7:		Line 7:
	[[File:CMIP5-LOCA-VIC_4.5_streamflow_P_16.png\|thumb\|700px\|Figure 2. Projected future annual streamflow change for the Colorado River at Lees Ferry compared to a 1971–2000 baseline, from an ensemble of 16 CMIP5 model projections under the moderate RCP4.5 emissions scenario with LOCA downscaling, and the resulting temperature and precipitation changes run through the VIC hydrologic model to simulate runoff changes. These 16 projections are ones showing smaller precipitation changes (both positive and negative) over the 21st century than the other 16 CMIP5-LOCA-VIC projections. The light blue lines are the 30-year running averages, plotted on the middle (16th) year, of the individual model projections of future streamflow change, with the median projection shown as the dark dashed line. The box-whiskers plot at rights show the distribution of the 30-year average values at 2055 (2041–2070). (Figure: J. Lukas, adapted from Lukas and Payton, 2020; Data: CMIP5-LOCA-VIC: N. Mizukami, NCAR; see Vano et al. 2020)]]		[[File:CMIP5-LOCA-VIC_4.5_streamflow_P_16.png\|thumb\|700px\|Figure 2. Projected future annual streamflow change for the Colorado River at Lees Ferry compared to a 1971–2000 baseline, from an ensemble of 16 CMIP5 model projections under the moderate RCP4.5 emissions scenario with LOCA downscaling, and the resulting temperature and precipitation changes run through the VIC hydrologic model to simulate runoff changes. These 16 projections are ones showing smaller precipitation changes (both positive and negative) over the 21st century than the other 16 CMIP5-LOCA-VIC projections. The light blue lines are the 30-year running averages, plotted on the middle (16th) year, of the individual model projections of future streamflow change, with the median projection shown as the dark dashed line. The box-whiskers plot at rights show the distribution of the 30-year average values at 2055 (2041–2070). (Figure: J. Lukas, adapted from Lukas and Payton, 2020; Data: CMIP5-LOCA-VIC: N. Mizukami, NCAR; see Vano et al. 2020)]]

	But there is now clear evidence that the hydrology of the Colorado River Basin is already systematically changing, and that the future hydrology will be substantially different than the past, as a result of anthropogenic climate change. While the gaged hydrology and paleohydrology can still provide important information about hydrologic variability to inform long-range planning, they cannot capture the likely future systematic changes in hydrology in the basin. Accordingly, recent basinwide planning activities (e.g., [[2012 Colorado River Basin Study]], [[2018 CRB Ten Tribes Partnership Tribal Water Study]]) and broader-scale Reclamation assessments ([[2021 SECURE Water Act reports]]) have analyzed scenarios of future hydrology derived from projections from global climate models (GCMs) ~~with additional hydrologic modeling~~.		But there is now clear evidence that the hydrology of the Colorado River Basin is already systematically changing, and that the future hydrology will be substantially different than the past, as a result of anthropogenic climate change. While the gaged hydrology and paleohydrology can still provide important information about hydrologic variability to inform long-range planning, they cannot capture the likely future systematic changes in hydrology in the basin. Accordingly, recent basinwide planning activities (e.g., [[2012 Colorado River Basin Study]], [[2018 CRB Ten Tribes Partnership Tribal Water Study]]) and broader-scale Reclamation assessments ([[2021 SECURE Water Act reports]]) have analyzed scenarios of future hydrology derived from projections from global climate models (GCMs).

	To generate such scenarios of future hydrology, researchers typically take the future changes in temperature and precipitation as output by multiple GCMs, and then translate those climate changes into basin runoff changes using a separate hydrologic model. Before being run through the hydrologic model, the relatively coarse-grained GCM output needs to be downscaled (e.g., from a 150-km grid to a 12-km grid) to match the spatial resolution of the finer-grained hydrologic model. (GCMs do in fact model the entire hydrologic cycle, but their coarse resolution, and resulting poor representation of mountainous topography, limits the reliability of the GCM's raw hydrologic output, e.g., soil moisture, snowpack, runoff, etc. Thus the need for a separate, finer-scale, hydrologic model.)		To generate such scenarios of future hydrology, researchers typically take the future changes in temperature and precipitation as output by multiple GCMs, and then translate those climate changes into basin runoff changes using a separate hydrologic model. Before being run through the hydrologic model, the relatively coarse-grained GCM output needs to be downscaled (e.g., from a 150-km grid to a 12-km grid) to match the spatial resolution of the finer-grained hydrologic model. (GCMs do in fact model the entire hydrologic cycle, but their coarse resolution, and resulting poor representation of mountainous topography, limits the reliability of the GCM's raw hydrologic output, e.g., soil moisture, snowpack, runoff, etc. Thus the need for a separate, finer-scale, hydrologic model.)
Line 13:		Line 13:
	As noted in [[Projected future climate]], all GCM projections of future climate regardless of emissions scenario indicate further increases in temperatures of the basin, and this warming by itself will increase evapotranspiration (ET) and reduce basin runoff, by an estimated 4-9% per degree F of warming. Precipitation, however, is the most important driver of runoff on a year-to-year basis, and the GCMs are in much less agreement regarding the direction of future precipitation change for the basin. In some projections of future basin hydrology, there is a sufficiently large increase in annual precipitation to overcome the effect of warming temperatures, and so runoff increases. But in most (65-90%) projections of future basin hydrology driven by GCMs, across many different studies, the impact of warming combined with the precipitation outcome leads to net declines in basin runoff over the next several decades.		As noted in [[Projected future climate]], all GCM projections of future climate regardless of emissions scenario indicate further increases in temperatures of the basin, and this warming by itself will increase evapotranspiration (ET) and reduce basin runoff, by an estimated 4-9% per degree F of warming. Precipitation, however, is the most important driver of runoff on a year-to-year basis, and the GCMs are in much less agreement regarding the direction of future precipitation change for the basin. In some projections of future basin hydrology, there is a sufficiently large increase in annual precipitation to overcome the effect of warming temperatures, and so runoff increases. But in most (65-90%) projections of future basin hydrology driven by GCMs, across many different studies, the impact of warming combined with the precipitation outcome leads to net declines in basin runoff over the next several decades.

	Figure 1 shows an ensemble of 32 simulations of changes in future Colorado River flow at Lees Ferry (i.e., Upper Basin runoff), from 32 GCM projections run under the moderate RCP4.5 emissions scenario, downscaled with the LOCA method and then run through the VIC hydrologic model. By the mid-21st century, streamflows have declined in more than two-thirds (21) of these projections, even though precipitation increases over the 21st century in most of the 32 projections. Figure 2 shows only the 16 simulations ~~with~~ smaller precipitation changes (up or down) over the 21st century~~. This reduced ensemble more clearly shows the impact of future warming on streamflow~~, ~~and deemphasizes~~ the potential for large future precipitation changes, since there is much less confidence in specific precipitation outcomes than in the overall warming.		Figure 1 shows an ensemble of 32 simulations of changes in future Colorado River flow at Lees Ferry (i.e., Upper Basin runoff), from 32 GCM projections run under the moderate RCP4.5 emissions scenario, downscaled with the LOCA method and then run through the VIC hydrologic model. By the mid-21st century, streamflows have declined in more than two-thirds (21) of these projections, even though precipitation increases over the 21st century in most of the 32 projections. Figure 2 shows only the 16 simulations assuming smaller precipitation changes (up or down) over the 21st century, thus deemphasizing the potential for large future precipitation changes since there is much less confidence in specific precipitation outcomes than in the overall warming. This reduced ensemble more clearly shows the impact of future warming on streamflow.

	==Data and tools==		==Data and tools==

JeffreyJLukas: /* Additional resources */

2024-10-21T22:09:05Z

Additional resources

← Older revision		Revision as of 18:09, 21 October 2024
Line 40:		Line 40:
	==Additional resources==		==Additional resources==

			===[https://wwa.colorado.edu/resources/colorado-river-resources/CRBreport Colorado River Basin Climate and Hydrology: State of the Science report]===
	[https://wwa.colorado.edu/publications/reports/CRBreport/ColoRiver_StateOfScience_WWA_2020_Chapter_11.pdf Chapter 11] of the State of the Science report details the projected future hydrology for the basin, in section 11.7, following section 11.6, which covers the projected future climate (temperature and precipitation changes). Chapter 11 also described the methods and data used in these projections: Global climate models (GCMs; 11.2); CMIP (11.3); Emissions scenarios (11.4); Downscaling (11.5). [https://wwa.colorado.edu/publications/reports/CRBreport/ColoRiver_StateOfScience_WWA_2020_Chapter_6.pdf Chapter 6] describes in detail the hydrologic models such as VIC that are used to translate the climate model output into hydrologic changes.		[https://wwa.colorado.edu/publications/reports/CRBreport/ColoRiver_StateOfScience_WWA_2020_Chapter_11.pdf Chapter 11] of the State of the Science report details the projected future hydrology for the basin, in section 11.7, following section 11.6, which covers the projected future climate (temperature and precipitation changes). Chapter 11 also described the methods and data used in these projections: Global climate models (GCMs; 11.2); CMIP (11.3); Emissions scenarios (11.4); Downscaling (11.5). [https://wwa.colorado.edu/publications/reports/CRBreport/ColoRiver_StateOfScience_WWA_2020_Chapter_6.pdf Chapter 6] describes in detail the hydrologic models such as VIC that are used to translate the climate model output into hydrologic changes.

JeffreyJLukas: /* Additional resources */

2024-10-21T22:08:10Z

Additional resources

← Older revision		Revision as of 18:08, 21 October 2024
Line 40:		Line 40:
	==Additional resources==		==Additional resources==

	~~===State of the Science Report===~~

	[https://wwa.colorado.edu/publications/reports/CRBreport/ColoRiver_StateOfScience_WWA_2020_Chapter_11.pdf Chapter 11] of the State of the Science report details the projected future hydrology for the basin, in section 11.7, following section 11.6, which covers the projected future climate (temperature and precipitation changes). Chapter 11 also described the methods and data used in these projections: Global climate models (GCMs; 11.2); CMIP (11.3); Emissions scenarios (11.4); Downscaling (11.5). [https://wwa.colorado.edu/publications/reports/CRBreport/ColoRiver_StateOfScience_WWA_2020_Chapter_6.pdf Chapter 6] describes in detail the hydrologic models such as VIC that are used to translate the climate model output into hydrologic changes.		[https://wwa.colorado.edu/publications/reports/CRBreport/ColoRiver_StateOfScience_WWA_2020_Chapter_11.pdf Chapter 11] of the State of the Science report details the projected future hydrology for the basin, in section 11.7, following section 11.6, which covers the projected future climate (temperature and precipitation changes). Chapter 11 also described the methods and data used in these projections: Global climate models (GCMs; 11.2); CMIP (11.3); Emissions scenarios (11.4); Downscaling (11.5). [https://wwa.colorado.edu/publications/reports/CRBreport/ColoRiver_StateOfScience_WWA_2020_Chapter_6.pdf Chapter 6] describes in detail the hydrologic models such as VIC that are used to translate the climate model output into hydrologic changes.

JeffreyJLukas: /* National Climate Change Viewer */

2024-10-21T16:28:25Z

National Climate Change Viewer

← Older revision		Revision as of 12:28, 21 October 2024
Line 31:		Line 31:

	===[https://www.usgs.gov/tools/national-climate-change-viewer-nccv National Climate Change Viewer]===		===[https://www.usgs.gov/tools/national-climate-change-viewer-nccv National Climate Change Viewer]===
	The National Climate Change Viewer (NCCV) allows users to generate zoomable change maps, time series, monthly climographs, and scatterplots for multiple climate and hydrology variables, including area-averaged runoff (in inches or cm). ~~The viewer's~~ analysis areas ~~are~~ river basins/watersheds (HUC2, HUC4, and HUC8)~~. All~~ projected climate ~~data are from the~~ MACA-downscaled CMIP5 ~~dataset~~ (~~all~~ 20 models)~~; the~~ hydrology variables such as runoff are derived from the USGS ~~Simple~~ Water-balance Model driven with the projected temperature and precipitation.		The National Climate Change Viewer (NCCV) allows users to generate zoomable change maps, time series, monthly climographs, and scatterplots for multiple climate and hydrology variables, including area-averaged runoff (in inches or cm). Before the Viewer loads, users select one of two sets of analysis areas: (1) states/counties, or (2) river basins/watersheds (HUC2, HUC4, and HUC8), and one of two projected climate datasets: (1) MACA-downscaled CMIP5 (20 models under RCP4.5 and RCP8.5 emissions), or (2) LOCA-downscaled CMIP6 (23 models under SSP2-4.5, SSP3-7.0, and SSP5-8.5 emissions). The hydrology variables such as runoff are derived from the USGS Monthly Water-balance Model (MWBM) driven with the projected temperature and precipitation.

	===[https://gdo-dcp.ucllnl.org/ GDO-DCHP: Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections]===		===[https://gdo-dcp.ucllnl.org/ GDO-DCHP: Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections]===

JeffreyJLukas: /* National Climate Change Viewer */

2024-10-21T16:13:32Z

National Climate Change Viewer

← Older revision		Revision as of 12:13, 21 October 2024
Line 30:		Line 30:
	The Future Boxplots allows users to generate boxplots of modeled historical and future area-averaged projected runoff (in inches) for user-selected points, rectangular areas, counties, and HUC8 watersheds.		The Future Boxplots allows users to generate boxplots of modeled historical and future area-averaged projected runoff (in inches) for user-selected points, rectangular areas, counties, and HUC8 watersheds.

	===[https://~~www2~~.usgs.gov/~~landresources/lcs~~/nccv~~/maca2/maca2_watersheds.html~~ National Climate Change Viewer]===		===[https://www.usgs.gov/tools/national-climate-change-viewer-nccv National Climate Change Viewer]===
	The National Climate Change Viewer (NCCV) allows users to generate zoomable change maps, time series, monthly climographs, and scatterplots for multiple climate and hydrology variables, including area-averaged runoff (in inches or cm). The viewer's analysis areas are river basins/watersheds (HUC2, HUC4, and HUC8). All projected climate data are from the MACA-downscaled CMIP5 dataset (all 20 models); the hydrology variables such as runoff are derived from the USGS Simple Water-balance Model driven with the projected temperature and precipitation.		The National Climate Change Viewer (NCCV) allows users to generate zoomable change maps, time series, monthly climographs, and scatterplots for multiple climate and hydrology variables, including area-averaged runoff (in inches or cm). The viewer's analysis areas are river basins/watersheds (HUC2, HUC4, and HUC8). All projected climate data are from the MACA-downscaled CMIP5 dataset (all 20 models); the hydrology variables such as runoff are derived from the USGS Simple Water-balance Model driven with the projected temperature and precipitation.

JeffreyJLukas: /* Climate Toolbox */

2024-10-21T16:11:07Z

Climate Toolbox

← Older revision		Revision as of 12:11, 21 October 2024
Line 22:		Line 22:
	<onlyinclude>		<onlyinclude>
	===[https://climatetoolbox.org Climate Toolbox]===		===[https://climatetoolbox.org Climate Toolbox]===
	The Climate Toolbox is a diverse set of interactive tools developed by researchers at U. Cal-Merced and partners. All projected climate data are from the MACA-downscaled CMIP5 dataset. The projections of hydrologic variables in Climate Toolbox are based on a reduced ensemble (10 vs. 20) of CMIP5-MACA climate projections (temperature and precipitation) that have been run through the VIC hydrologic model. Note that with 10 ~~members~~, this ensemble ~~of hydrologic projections~~ may not reflect the full range of potential climate (and hydrology) futures shown across all CMIP5 projections.		The Climate Toolbox is a diverse set of interactive tools developed by researchers at U. Cal-Merced and partners. All projected climate data are from the MACA-downscaled CMIP5 dataset. The projections of hydrologic variables in Climate Toolbox are based on a reduced ensemble (10 GCMs vs. 20 GCMs) of CMIP5-MACA climate projections (temperature and precipitation) that have been run through the VIC hydrologic model. Note that with only 10 hydrologic projections, this particular ensemble may not reflect the full range of potential climate (and hydrology) futures shown across all CMIP5 projections.

	====[https://climatetoolbox.org/tool/future-streamflows Climate Toolbox - Future Streamflows]====		====[https://climatetoolbox.org/tool/future-streamflows Climate Toolbox - Future Streamflows]====
Line 28:		Line 28:

	====[https://climatetoolbox.org/tool/future-boxplots Climate Toolbox - Future Boxplots]====		====[https://climatetoolbox.org/tool/future-boxplots Climate Toolbox - Future Boxplots]====
	The Future Boxplots allows users to generate boxplots of modeled historical and future area-averaged projected runoff (in inches) for user-selected points, rectangular areas, counties, and HUC8 watersheds.		The Future Boxplots allows users to generate boxplots of modeled historical and future area-averaged projected runoff (in inches) for user-selected points, rectangular areas, counties, and HUC8 watersheds.

	===[https://www2.usgs.gov/landresources/lcs/nccv/maca2/maca2_watersheds.html National Climate Change Viewer]===		===[https://www2.usgs.gov/landresources/lcs/nccv/maca2/maca2_watersheds.html National Climate Change Viewer]===

JeffreyJLukas: /* Overview */

2024-10-21T16:09:46Z

Overview

← Older revision		Revision as of 12:09, 21 October 2024
Line 9:		Line 9:
	But there is now clear evidence that the hydrology of the Colorado River Basin is already systematically changing, and that the future hydrology will be substantially different than the past, as a result of anthropogenic climate change. While the gaged hydrology and paleohydrology can still provide important information about hydrologic variability to inform long-range planning, they cannot capture the likely future systematic changes in hydrology in the basin. Accordingly, recent basinwide planning activities (e.g., [[2012 Colorado River Basin Study]], [[2018 CRB Ten Tribes Partnership Tribal Water Study]]) and broader-scale Reclamation assessments ([[2021 SECURE Water Act reports]]) have analyzed scenarios of future hydrology derived from projections from global climate models (GCMs) with additional hydrologic modeling.		But there is now clear evidence that the hydrology of the Colorado River Basin is already systematically changing, and that the future hydrology will be substantially different than the past, as a result of anthropogenic climate change. While the gaged hydrology and paleohydrology can still provide important information about hydrologic variability to inform long-range planning, they cannot capture the likely future systematic changes in hydrology in the basin. Accordingly, recent basinwide planning activities (e.g., [[2012 Colorado River Basin Study]], [[2018 CRB Ten Tribes Partnership Tribal Water Study]]) and broader-scale Reclamation assessments ([[2021 SECURE Water Act reports]]) have analyzed scenarios of future hydrology derived from projections from global climate models (GCMs) with additional hydrologic modeling.

	To generate such scenarios of future hydrology, researchers take ~~outputs from multiple GCMs, i.e., specific~~ future changes in temperature and precipitation ~~from each model~~, and then translate those climate changes into basin runoff changes using a separate hydrologic model. Before being run through the hydrologic model, the relatively coarse-grained GCM output needs to be downscaled (e.g., from a 150-km grid to a 12-km grid) to match the spatial resolution of the finer-grained hydrologic model. (GCMs do model the entire hydrologic cycle, but their coarse resolution, and resulting poor representation of ~~complex~~ topography, limits the reliability of the GCM's raw hydrologic output, e.g., soil moisture, snowpack, runoff, etc. Thus the need for a separate, finer-scale, hydrologic model.)		To generate such scenarios of future hydrology, researchers typically take the future changes in temperature and precipitation as output by multiple GCMs, and then translate those climate changes into basin runoff changes using a separate hydrologic model. Before being run through the hydrologic model, the relatively coarse-grained GCM output needs to be downscaled (e.g., from a 150-km grid to a 12-km grid) to match the spatial resolution of the finer-grained hydrologic model. (GCMs do in fact model the entire hydrologic cycle, but their coarse resolution, and resulting poor representation of mountainous topography, limits the reliability of the GCM's raw hydrologic output, e.g., soil moisture, snowpack, runoff, etc. Thus the need for a separate, finer-scale, hydrologic model.)

	As noted in [[Projected future climate]], all GCM projections of future climate regardless of emissions scenario indicate further increases in temperatures of the basin, and this warming by itself will increase evapotranspiration (ET) and reduce basin runoff, by an estimated 4-9% per degree F of warming. Precipitation, however, is the most important driver of runoff on a year-to-year basis, and the GCMs are in much less agreement regarding the direction of future precipitation change for the basin. In some projections of future basin hydrology, there is a sufficiently large increase in annual precipitation to overcome the effect of warming temperatures, and so runoff increases. But in most (65-90%) projections of future basin hydrology driven by GCMs, across many different studies, the impact of warming combined with the precipitation outcome leads to net declines in basin runoff over the next several decades.		As noted in [[Projected future climate]], all GCM projections of future climate regardless of emissions scenario indicate further increases in temperatures of the basin, and this warming by itself will increase evapotranspiration (ET) and reduce basin runoff, by an estimated 4-9% per degree F of warming. Precipitation, however, is the most important driver of runoff on a year-to-year basis, and the GCMs are in much less agreement regarding the direction of future precipitation change for the basin. In some projections of future basin hydrology, there is a sufficiently large increase in annual precipitation to overcome the effect of warming temperatures, and so runoff increases. But in most (65-90%) projections of future basin hydrology driven by GCMs, across many different studies, the impact of warming combined with the precipitation outcome leads to net declines in basin runoff over the next several decades.

JeffreyJLukas: /* GDO-DCHP: Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections */

2024-10-21T15:53:11Z

GDO-DCHP: Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections

← Older revision		Revision as of 11:53, 21 October 2024
Line 34:		Line 34:

	===[https://gdo-dcp.ucllnl.org/ GDO-DCHP: Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections]===		===[https://gdo-dcp.ucllnl.org/ GDO-DCHP: Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections]===
	This portal allows downloading of the CMIP5-LOCA-VIC projected hydrology dataset~~, from which~~ Figures 1 and 2 ~~are derived~~, in netCDF or ASCII (text) format. (There are no visualization tools on the site.) The tab "Projections: Complete Archive" allows users to download the entire dataset for all of CONUS; most users will want to select the "Projections: Subset Request" tab and step through the tabs to select the time period, area of interest, dataset and models, and data format.		This portal allows downloading of the CMIP5-LOCA-VIC projected hydrology dataset (the data source for Figures 1 and 2), in netCDF or ASCII (text) format. There are no visualization tools on the site. The tab "Projections: Complete Archive" allows users to download the entire dataset for all of the contiguous U.S. (CONUS); most users will want to select the "Projections: Subset Request" tab and step through the tabs to select the time period, area of interest, dataset and models, and data format.

	</onlyinclude>		</onlyinclude>

JeffreyJLukas: /* Overview */

2024-04-29T21:19:54Z

Overview

← Older revision		Revision as of 17:19, 29 April 2024
Line 3:		Line 3:
	Traditionally, long-range water planning in the Colorado River Basin and elsewhere has operated under the assumption of ''stationarity'', that the future would closely resemble the past, at least in a statistical sense (average and variability). Thus, Reclamation and other water agencies relied on resampling the historical gaged hydrology (see [[Streamflow]]) to construct scenarios of future hydrology. Starting in the 1970s, and especially after 2000, much longer records of streamflow obtained from [[Paleohydrology]] have provided an expanded perspective on past hydrologic variability beyond that available in the gaged hydrology.		Traditionally, long-range water planning in the Colorado River Basin and elsewhere has operated under the assumption of ''stationarity'', that the future would closely resemble the past, at least in a statistical sense (average and variability). Thus, Reclamation and other water agencies relied on resampling the historical gaged hydrology (see [[Streamflow]]) to construct scenarios of future hydrology. Starting in the 1970s, and especially after 2000, much longer records of streamflow obtained from [[Paleohydrology]] have provided an expanded perspective on past hydrologic variability beyond that available in the gaged hydrology.

	[[File:CMIP5-LOCA-VIC_4.5_streamflow_all_32.png\|thumb\|700px\|Figure 1. Projected future annual streamflow change for the Colorado River at Lees Ferry compared to a 1971–2000 baseline, from an ensemble of 32 CMIP5 model projections under the moderate RCP4.5 emissions scenario with LOCA downscaling, and the resulting temperature and precipitation changes run through the VIC hydrologic model to simulate runoff changes. The light blue lines are the 30-year running averages, plotted on the middle (~~15th~~) year, of the individual model projections of future streamflow change, with the median projection shown as the dark dashed line. The box-whiskers plot at rights show the distribution of the 30-year average values at 2055 (2041–2070). (Figure: J. Lukas, adapted from Lukas and Payton, 2020; Data: CMIP5-LOCA-VIC: N. Mizukami, NCAR; see Vano et al. 2020)]]		[[File:CMIP5-LOCA-VIC_4.5_streamflow_all_32.png\|thumb\|700px\|Figure 1. Projected future annual streamflow change for the Colorado River at Lees Ferry compared to a 1971–2000 baseline, from an ensemble of 32 CMIP5 model projections under the moderate RCP4.5 emissions scenario with LOCA downscaling, and the resulting temperature and precipitation changes run through the VIC hydrologic model to simulate runoff changes. The light blue lines are the 30-year running averages, plotted on the middle (16th) year, of the individual model projections of future streamflow change, with the median projection shown as the dark dashed line. The box-whiskers plot at rights show the distribution of the 30-year average values at 2055 (2041–2070). (Figure: J. Lukas, adapted from Lukas and Payton, 2020; Data: CMIP5-LOCA-VIC: N. Mizukami, NCAR; see Vano et al. 2020)]]

	[[File:CMIP5-LOCA-VIC_4.5_streamflow_P_16.png\|thumb\|700px\|Figure 2. Projected future annual streamflow change for the Colorado River at Lees Ferry compared to a 1971–2000 baseline, from an ensemble of 16 CMIP5 model projections under the moderate RCP4.5 emissions scenario with LOCA downscaling, and the resulting temperature and precipitation changes run through the VIC hydrologic model to simulate runoff changes. These 16 projections are ones showing smaller precipitation changes (both positive and negative) over the 21st century than the other 16 CMIP5-LOCA-VIC projections. The light blue lines are the 30-year running averages, plotted on the middle (~~15th~~) year, of the individual model projections of future streamflow change, with the median projection shown as the dark dashed line. The box-whiskers plot at rights show the distribution of the 30-year average values at 2055 (2041–2070). (Figure: J. Lukas, adapted from Lukas and Payton, 2020; Data: CMIP5-LOCA-VIC: N. Mizukami, NCAR; see Vano et al. 2020)]]		[[File:CMIP5-LOCA-VIC_4.5_streamflow_P_16.png\|thumb\|700px\|Figure 2. Projected future annual streamflow change for the Colorado River at Lees Ferry compared to a 1971–2000 baseline, from an ensemble of 16 CMIP5 model projections under the moderate RCP4.5 emissions scenario with LOCA downscaling, and the resulting temperature and precipitation changes run through the VIC hydrologic model to simulate runoff changes. These 16 projections are ones showing smaller precipitation changes (both positive and negative) over the 21st century than the other 16 CMIP5-LOCA-VIC projections. The light blue lines are the 30-year running averages, plotted on the middle (16th) year, of the individual model projections of future streamflow change, with the median projection shown as the dark dashed line. The box-whiskers plot at rights show the distribution of the 30-year average values at 2055 (2041–2070). (Figure: J. Lukas, adapted from Lukas and Payton, 2020; Data: CMIP5-LOCA-VIC: N. Mizukami, NCAR; see Vano et al. 2020)]]

	But there is now clear evidence that the hydrology of the Colorado River Basin is already systematically changing, and that the future hydrology will be substantially different than the past, as a result of anthropogenic climate change. While the gaged hydrology and paleohydrology can still provide important information about hydrologic variability to inform long-range planning, they cannot capture the likely future systematic changes in hydrology in the basin. Accordingly, recent basinwide planning activities (e.g., [[2012 Colorado River Basin Study]], [[2018 CRB Ten Tribes Partnership Tribal Water Study]]) and broader-scale Reclamation assessments ([[2021 SECURE Water Act reports]]) have analyzed scenarios of future hydrology derived from projections from global climate models (GCMs) with additional hydrologic modeling.		But there is now clear evidence that the hydrology of the Colorado River Basin is already systematically changing, and that the future hydrology will be substantially different than the past, as a result of anthropogenic climate change. While the gaged hydrology and paleohydrology can still provide important information about hydrologic variability to inform long-range planning, they cannot capture the likely future systematic changes in hydrology in the basin. Accordingly, recent basinwide planning activities (e.g., [[2012 Colorado River Basin Study]], [[2018 CRB Ten Tribes Partnership Tribal Water Study]]) and broader-scale Reclamation assessments ([[2021 SECURE Water Act reports]]) have analyzed scenarios of future hydrology derived from projections from global climate models (GCMs) with additional hydrologic modeling.
Line 13:		Line 13:
	As noted in [[Projected future climate]], all GCM projections of future climate regardless of emissions scenario indicate further increases in temperatures of the basin, and this warming by itself will increase evapotranspiration (ET) and reduce basin runoff, by an estimated 4-9% per degree F of warming. Precipitation, however, is the most important driver of runoff on a year-to-year basis, and the GCMs are in much less agreement regarding the direction of future precipitation change for the basin. In some projections of future basin hydrology, there is a sufficiently large increase in annual precipitation to overcome the effect of warming temperatures, and so runoff increases. But in most (65-90%) projections of future basin hydrology driven by GCMs, across many different studies, the impact of warming combined with the precipitation outcome leads to net declines in basin runoff over the next several decades.		As noted in [[Projected future climate]], all GCM projections of future climate regardless of emissions scenario indicate further increases in temperatures of the basin, and this warming by itself will increase evapotranspiration (ET) and reduce basin runoff, by an estimated 4-9% per degree F of warming. Precipitation, however, is the most important driver of runoff on a year-to-year basis, and the GCMs are in much less agreement regarding the direction of future precipitation change for the basin. In some projections of future basin hydrology, there is a sufficiently large increase in annual precipitation to overcome the effect of warming temperatures, and so runoff increases. But in most (65-90%) projections of future basin hydrology driven by GCMs, across many different studies, the impact of warming combined with the precipitation outcome leads to net declines in basin runoff over the next several decades.

	Figure 1 shows an ensemble of 32 simulations of changes in future Colorado River flow at Lees Ferry (i.e., Upper Basin runoff), from 32 GCM projections run under the moderate RCP4.5 emissions scenario, downscaled with the LOCA method and then run through the VIC hydrologic model. By the mid-21st century, streamflows have declined in more than two-thirds (21) of these projections, even though precipitation increases over the 21st century in most of the 32 projections. Figure 2 shows only the 16 simulations with smaller precipitation changes (up or down) over the 21st century. This reduced ensemble more clearly shows the impact of future warming on streamflow, and deemphasizes the potential for large future precipitation changes, since there is much less confidence in specific precipitation outcomes than in the overall warming.		Figure 1 shows an ensemble of 32 simulations of changes in future Colorado River flow at Lees Ferry (i.e., Upper Basin runoff), from 32 GCM projections run under the moderate RCP4.5 emissions scenario, downscaled with the LOCA method and then run through the VIC hydrologic model. By the mid-21st century, streamflows have declined in more than two-thirds (21) of these projections, even though precipitation increases over the 21st century in most of the 32 projections. Figure 2 shows only the 16 simulations with smaller precipitation changes (up or down) over the 21st century. This reduced ensemble more clearly shows the impact of future warming on streamflow, and deemphasizes the potential for large future precipitation changes, since there is much less confidence in specific precipitation outcomes than in the overall warming.

	==Data and tools==		==Data and tools==

JeffreyJLukas: /* National Climate Change Viewer */

2023-10-18T21:01:24Z

National Climate Change Viewer

← Older revision		Revision as of 17:01, 18 October 2023
Line 31:		Line 31:

	===[https://www2.usgs.gov/landresources/lcs/nccv/maca2/maca2_watersheds.html National Climate Change Viewer]===		===[https://www2.usgs.gov/landresources/lcs/nccv/maca2/maca2_watersheds.html National Climate Change Viewer]===
	The National Climate Change Viewer (NCCV) allows users to generate zoomable change maps, time series, monthly climographs, and scatterplots for multiple climate and hydrology variables, including area-averaged runoff (in inches or cm). The viewer's analysis areas are river basins/watersheds (HUC2, HUC4, and HUC8). All projected climate data are from the MACA-downscaled CMIP5 dataset (all 20 models); the hydrology variables such as runoff are derived from ~~a simple water~~-balance ~~model~~ driven with the projected temperature and precipitation.		The National Climate Change Viewer (NCCV) allows users to generate zoomable change maps, time series, monthly climographs, and scatterplots for multiple climate and hydrology variables, including area-averaged runoff (in inches or cm). The viewer's analysis areas are river basins/watersheds (HUC2, HUC4, and HUC8). All projected climate data are from the MACA-downscaled CMIP5 dataset (all 20 models); the hydrology variables such as runoff are derived from the USGS Simple Water-balance Model driven with the projected temperature and precipitation.

	===[https://gdo-dcp.ucllnl.org/ GDO-DCHP: Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections]===		===[https://gdo-dcp.ucllnl.org/ GDO-DCHP: Downscaled CMIP3 and CMIP5 Climate and Hydrology Projections]===