Grantee Research Project Results
2012 Progress Report: Assessing the Impact of a Warmer Climate on Stream Water Quality Across theMountainous Western United States.
EPA Grant Number: R834191Title: Assessing the Impact of a Warmer Climate on Stream Water Quality Across theMountainous Western United States.
Investigators: Stewart-Frey, Iris , Maurer, Edwin
Institution: Santa Clara University
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2009 through August 31, 2012 (Extended to August 31, 2013)
Project Period Covered by this Report: September 1, 2011 through August 31,2012
Project Amount: $250,000
RFA: Consequences of Global Change for Water Quality (2008) RFA Text | Recipients Lists
Research Category: Aquatic Ecosystems , Ecological Indicators/Assessment/Restoration , Watersheds , Water , Climate Change
Objective:
Stream temperature, dissolved oxygen (DO), and sediment concentrations play a crucial role in the life cycle and habitat distribution of aquatic species, determine the suitability of water resources for human use, and are expected to be affected by projected climatic changes. Projections of future stream water quality parameters are particularly important for regions such as the mountainous western United States where water resources already are limited, air temperatures are projected to warm significantly, and runs of important cold water species, such as salmon and trout, are threatened. The objective of this work, then, is to project changes in water flow and water quality for the mountainous areas of the western United States through the end of the century using an ensemble of downscaled General Circulation Model (GCM) output (16 models) and two emission scenarios, to drive an established watershed model (Soil and Water Assessment Tool [SWAT]) with an improved stream temperature model. The output is analyzed to further the understanding of changes in hydrologic flows components (precipitation, evapotranspiration, snowmelt, streamflow, surface flow, subsurface flow, soil and groundwater storage) and water quality across GCM models, emission scenarios, geological and elevational differences, and on different temporal and spatial scales. The understanding gained from this project and the sub-basin modeling scale aid in identifying the critical areas in watersheds for best management practices with the goal of maintaining or improving water quality and fish and wildlife habitat.
Progress Summary:
A new stream temperature model has been developed and incorporated into the SWAT model for stream temperature simulation at the sub-basin level; with the new model, a flow-weighted stream temperature is calculated to preserve the local contribution. Water flow and quality simulations have been completed for the Sierra Nevada and upper Colorado River. We also have completed water flow and quality simulations for the Sierra Nevada and upper Colorado River Basin (UCRB) watersheds. Main outcomes from this work are:
- Based on a 16-model ensemble of downscaled GCM output, temperatures in the Sierra Nevada and Upper Colorado River Basin (UCRB) are expected to increase while precipitation projections vary between GCMs with a median decrease.
- The SWAT hydrologic simulations for the Sierra Nevada (CA) showed that projected climatic warming and earlier snowmelt impacts not only streamflow, but evapotranspiration, surface, and subsurface flows, such that less water is available in spring and summer. By the 2080s, 89% of the subwatersheds are expected to have a snowmelt contribution that is less than half of average historical snowpack. Annual streamflow are likely to be reduced, especially at mid-elevations.
- A new stream temperature model provides enhanced empirical simulation of stream temperature, by accounting for local heat contributions, heat transfer with water routing, and heat exchange when flowing through the stream. The model, which is not dependent on any empirical relationships between air and stream and does not require more information beyond what already is provided by the user, is better able to capture water temperature in mountain streams where warmer temperatures result in increased snowmelt.
- For the highly seasonal, water-limited, and mountainous basins such as exist in the Sierra Nevada (CA), significant changes in water quality can be expected under future climates. These changes appear especially significant for the spring and summer seasons and include stream temperature increases by up to 6 ºC for summer, reaching close to 30 ºC in the lower elevation reaches, decreases of DO by 2-12%, and overall decreases in sediment concentrations.
- For the UCRB, streamflow changes propagate from headwaters to Lee’s Ferry outflow. Under projected climatic changes, spring streamflow, an important contribution to annual flow, is likely to decrease by 20-90%. Snowmelt is likely to decrease by up to 80% throughout the mid and low elevations of the UCRB. The lower elevation areas where the largest decreases in spring streamflow and snowmelt are expected, are the most likely to stay or become arid landscapes, while the highest elevations are likely to remain mostly humid.
Future Activities:
We are preparing the hydrologic and water quality simulations for the Columbia river basin using SWAT and our new stream temperature model. In addition, we are planning to assess the surface hydrology and water quality modeling results for the ensemble of GCMs, different emission scenarios, different temporal and regional scales, as well as from region to region. The impact of projected climatic changes on water flow and quality for both human and ecosystem use will be evaluated.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
| Other project views: | All 26 publications | 10 publications in selected types | All 10 journal articles |
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Ficklin DL, Stewart IT, Maurer EP. Projections of 21st century Sierra Nevada local hydrologic flow components using an ensemble of General Circulation Models. Journal of the American Water Resources Association 2012;48(6):1104-1125. |
R834191 (2011) R834191 (2012) R834191 (Final) |
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Ficklin DL, Luo Y, Stewart IT, Maurer EP. Development and application of a hydroclimatological stream temperature model within the Soil and Water Assessment Tool. Water Resources Research 2012;48:W01511. |
R834191 (2011) R834191 (2012) R834191 (Final) |
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Ficklin DL, Stewart IT, Maurer EP. Effects of projected climate change on the hydrology in the Mono Lake Basin, California. Climatic Change 2013;116(1):111-131. |
R834191 (2011) R834191 (2012) R834191 (Final) |
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Supplemental Keywords:
climate change, streamflow, streamflow timing, stream temperature, water quality, western United States, hydrology, SWAT, stream temperature model;, RFA, Air, Atmosphere, Air Pollution Effects, climate change, water quality, environmental monitoring, climate modelsRelevant Websites:
Iris Stewart-Frey
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.