Watershed modeling to assess the sensitivity of streamflow, nutrient, and sediment loads to climate change and urban development in 20 U.S. watersheds

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 scenarios. The study uses a scenario-analysis approach with a consistent set of watershed models and scenarios applied to multiple locations throughout the nation. Watershed simulations were conducted using the Soil Water Assessment Tool (SWAT). Scenarios of future climate change were developed based on statistically and dynamically downscaled climate model simulations representative of mid 21stcentury (2041−2070). Scenarios of urban and residential development for this same period were based on housing density projections from EPA’s Integrated Climate and Land Use Scenarios (ICLUS) project. Future changes in agriculture and human use and management of water were not evaluated. Results provide an improved understanding of the complex and context-dependent relationships between climate change, land-use change, and water resources in different regions of the nation. As a first-order conclusion, results indicate that in many locations future conditions are likely to be different from past experience. Results also provide a plausible envelope on the range of streamflow and water quality responses to mid-21st century climate change and urban development in different regions of the nation. In addition, in many study areas the simulations suggest a likely direction of change of streamflow and water quality endpoints. This information is useful to inform and guide the development of response strategies for managing risk.

Impact/Purpose

This study assesses 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. Information will improve the ability of EPA and EPA clients to assess and manage climate-related risk to water resources.

Citation

Johnson, T., J. Butcher, AND C. Weaver. Watershed modeling to assess the sensitivity of streamflow, nutrient, and sediment loads to climate change and urban development in 20 U.S. watersheds. Consortium of Universities for the Advancement of Hydrologic Sciences (CUAHSI), NA, DC, January 23, 2014.

• CUAHSI_20WATERSHEDS_V5_508 TAGGED.PDF (PDF)  (NA  pp, 1.4 MB, about PDF)