US EPA

EPA has released for independent external peer review and public comment a draft report titled, Watershed Modeling to Assess the Sensitivity of Streamflow, Nutrient, and Sediment Loads to Potential Climate Change and Urban Development in 20 U.S. Watersheds. This is a draft document that intends to characterize the sensitivity of streamflow, nutrient (nitrogen and phosphorus), and sediment loading in different regions of the nation to a range of plausible mid-21st Century climate change and urban development scenarios.

Watershed modeling was conducted in 20 large, U.S. watersheds to assess the sensitivity of streamflow, nutrient (nitrogen and phosphorus), and sediment loading to a range of plausible mid-21st Century climate change and urban development scenarios in different regions of the nation. This draft report provides a summary of simulation results. The model simulations characterize the sensitivity of streamflow, nutrient (nitrogen and phosphorus), and sediment loading to a range of plausible mid-21st Century climate change and urban development. Results show a high degree of variability in the response throughout the nation. Results also provide an improved understanding of methodological challenges associated with integrating existing tools and datasets to address these scientific questions. This provides guidance for improving how existing models and datasets can be used for assessing climate change impacts on watersheds.

There is growing concern about the potential effects of climate change on water resources. Watershed modeling was conducted in 20 large, U.S. watersheds to characterize the sensitivity of streamflow, nutrient (nitrogen and phosphorus), and sediment loading to a range of plausible mid-21st Century climate change and urban development. The study also provides an improved understanding of methodological challenges associated with integrating existing tools (e.g., climate models, downscaling approaches, and watershed models) and datasets to address these scientific questions. Study sites were selected to represent a range of geographic, hydrologic, and climatic characteristics throughout the nation. Watershed simulations were conducted using the Soil Water Assessment Tool (SWAT) and Hydrologic Simulation Program- FORTRAN (HSPF) models.

Simulation results illustrate a high degree of variability in the response of different streamflow and water quality attributes to climate change throughout the nation. Results are also illustrate sensitivity to methodological choices such as different approaches for downscaling global climate change simulations and use of different watershed models. This understanding provides guidance for improving how existing models and datasets can be used for assessing climate change impacts on watersheds.

This report presents a summary of simulation results. The report is technical in nature but results are of broad interest water and watershed managers, urban or regional planners, government officials, and scientists and engineers interested in the potential implications of climate change on streamflow and water quality in different regions of the nation.

Projected changes in climate during the next century could cause or contribute to increased flooding, drought, water quality degradation, and ecosystem impairment.

Following a letter peer review, the report will be updated and posted on the EPA Web site.

U.S. EPA. Watershed Modeling to Assess the Sensitivity of Streamflow, Nutrient, and Sediment Loads to Potential Climate Change and Urban Development in 20 U.S. Watersheds (External Review Draft). U.S. Environmental Protection Agency, Washington, DC, 2013.

Comments on the assessment may be submitted and reviewed using the e-Government Regulations.gov Web site. From the site, select Environmental Protection Agency and the key word EPA-HQ-ORD-2012-0879 (for the docket ID).