New Data Added to EPA’s Nitrogen and Phosphorus Data Access Tool

EPA has added updated U.S. Geological Survey (USGS) SPAtially Referenced Regressions On Watershed attributes (SPARROW) data to EPA’s Nitrogen and Phosphorus Data Access Tool (NPDAT), a tool intended to help states develop effective nitrogen and phosphorus source reduction strategies. SPARROW is a GIS-based watershed model that integrates statistical and mechanistic modeling approaches to simulate long-term mean annual stream nutrient loads as a function of a wide range of known sources and factors affecting nutrient fate and transport.

USGS recently completed syntheses of the results from 12 independently-calibrated regional-scale SPARROW models that describe water quality conditions throughout major river basins of the conterminous U.S. based on nitrogen and phosphorus sources from 2002. Two data layers of EPA’s data access tool – one for nitrogen and one for phosphorus – now provide an approximate yet regionally consistent synthesis of the locations of the largest contributing sources.

The SPARROW geospatial layers can be used to prioritize watersheds for targeting nutrient reduction activities (such as stream monitoring) to the areas that account for a substantial portion of nutrient loads, and to develop state nitrogen and phosphorus pollution reduction strategies. This information is relevant to the protection of downstream coastal waters, such as the Gulf of Mexico, and to local receiving streams and reservoirs.

The NPDAT tool, with updated SPARROW layers, is available at: