Climate change projections indicate a steady increase in temperature progressing through the 21st century, generally resulting in snowpack reductions, changes to the timing of snowmelt, altered streamflows, and reductions in soil moisture, all of which could affect water management, agriculture, recreation, hazard mitigation, and ecosystems across the nation. Despite some widespread similarities in climate change trends, climate change will affect specific water basins in the U.S. differently, based on the particular hydrologic and geologic conditions in that area.
New USGS modeling studies project changes in water availability due to climate change at the local level. So far, the USGS has applied these models to fourteen basins, including:
- Sprague River Basin, Oregon
- Sagehen Creek Basin, California
- Feather River Basin, California
- Naches River Basin, Washington
- Yampa River Basin, Colorado
- East River Basin, Colorado
- Black Earth Creek Basin, Wisconsin
- Flint River Basin, Georgia
- Pomperaug River Watershed, Connecticut
- Clear Creek Basin, Iowa
- Cathance Stream Basin, Maine
- Trout Lake Basin, Wisconsin
- Starkweather Coulee Basin, North Dakota
- South Fork of the Flathead River, Montana
"The advantage of these studies is that they demonstrate that there is not just one hydrological response to climate change: the predictions account for essential local factors that will govern the timing, severity, and type of impact, whether it be water shortage, drought, or flood," said USGS Director Marcia McNutt. "This is exactly the sort of information communities need to know now, because we are unlikely to see a 'water-as-usual' future."
These local projections are based on General Circulation Models (GCM) that predict how climate change will affect temperature, precipitation, and emissions for large regional areas. The USGS's Precipitation Runoff Modeling System (PRMS) applies information from the downscaled GCM projections to local watersheds, where impacts of climate change on water availability will depend on local conditions. These local-scale hydrologic projections will allow managers to plan for changes in water resources that are specific to their area.
For example, the USGS models project that changes to snow pack in the Sprague River Basin in Oregon could cause annual peak streamflows to occur earlier in the spring as overall basin storage decreases, which may force managers to modify storage operation and reprioritize water deliveries for environmental and human needs. Reduced snowpack in headwaters of the Colorado River could affect the amount and timing of streamflow to the Colorado River and also impact important recreation areas. Portions of Maine may see higher streamflows which could affect populations of endangered Atlantic salmon. Areas of the already drought-stressed Flint River Basin, one of Atlanta's primary drinking water supplies, are projected to become even drier.
The results for each basin present a complex story due to uncertainty associated with the future climate projections and their effect on the hydrological response of the different geographical regions of the nation.
Detailed information about watershed responses to climate change can be found at http://pubs.usgs.gov/sir/2011/5077/. Additionally, a collection of USGS studies that contributed to these basin-wide analyses was published in the journal Earth Interactions and can be found at http://journals.ametsoc.org/page/Watershed.
The downscaled GCM models are obtained from the World Climate Research Programme's Coupled Model Intercomparison Project phase 3 multi-model dataset archive. The USGS PRMS models were developed as part of the USGS National Research Program (NRP) in cooperation with USGS Water Science Centers. The NRP develops new information, theories, and techniques to anticipate, understand, and solve problems facing resources managers and is a national leader in understanding the effects of climate change on water resources.
These USGS models are just one of several tools developed and used by agencies within the Department of the Interior to study potential impacts from climate change and to provide tools to resource managers to adapt to those changes. For example, the Bureau of Reclamation recently unveiled a user-friendly tool for calculating future streamflow and water supplies at 195 sites in the western United States to help increase accessibility of science-based information and ease understanding of how climate variations will impact water availability for local communities.
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