BASINS CAT (Better Assessment Science Integrating Point & Non-Point Sources Climate Assessment Tool)

Created: 7/28/2017 - Updated: 2/27/2020


BASINS was developed by the EPA to integrate environmental data, analysis tools, and watershed and water quality models to help inform watershed management and total maximum daily load (TMDL) development efforts. BASINS is a desktop application that utilizes GIS capabilities to compare how land use change and various management practices affect water quality. Through BASINS, users can access national and local data related to watersheds, and can apply assessment and planning tools and run nonpoint loading and water quality models. BASINS incorporates four types of data into simulation models: cartographic data showing administrative and hydrologic boundaries and road systems; environmental background data that includes information on soil characteristics, land use, and stream hydrography; monitoring data on water quality, streamflow, and groundwater; and point source data regarding discharge location, the type of facility, and estimated loading. BASINS also includes a number of environmental and utility assessment tools to help users evaluate water quality and pollution issues, identify data gaps and monitoring needs, and develop further watershed modeling tools.

BASINS CAT enhances the existing capability of BASINS by allowing users to assess how climate change may interact with land use and management changes to affect watersheds and water systems. Using BASINS CAT, users can simulate various climate change scenarios by adjusting historical temperature and precipitation data, allowing simulations of short- or long-term climate change, as well as evaluation of how variable seasonal or monthly conditions affect hydrological and water quality parameters. Users can also model impacts from increasing frequency of precipitation events. Regional, local, and state agencies can use BASINS CAT to perform climate-informed watershed and water quality modeling. Information from BASINS CAT can be used in watershed management, total maximum daily load (TMDL) development, coastal management, nonpoint source pollution programs, water quality monitoring, and National Pollutant Discharge Elimination System (NPDES) permitting, as well as to assess watershed sensitivity to climate change and to develop robust management strategies to help watersheds adapt to changing climate conditions.

Example in use: BASINS CAT has been applied to meet various watershed modeling needs across diverse regions of the United States. In the eastern United States, it has been used to create precipitation scenarios for use in conjunction with the Storm Water Management Model (SWMM), informing a stormwater runoff and mitigation assessment for an urban area along the Upper Roanoke River in Virginia. BASINS CAT was also used to analyze interactions between urbanization, climate change, and stormwater runoff volume and pollution in the Western Branch of the Patuxent River in Maryland. This particular study evaluated how shifts in precipitation volume, event intensity, and total impervious cover influenced stormwater runoff and pollutant loads. In the western United States, BASINS CAT has been used to analyze how water quality and flow in the Tualatin River in Oregon may change in response to altered precipitation regimes, and to analyze how streamflow may respond to shifts in the duration and magnitude of drought periods in California.

Phase of Adaptation: Assessment, Planning, Integration, Sharing



Land managers, natural resource managers, planners, engineers, scientists


The Environmental Protection Agency has ten Regional offices, each of which is responsible for the execution of the Agency's programs within several states and territories.