Point-Source Nutrient Loads to Streams of the Conterminous United States, 2012

The U.S. Geological Survey (USGS) developed a spatial water-quality model called SPAtially Referenced Regressions On Watershed attributes (SPARROW) to estimate the major sources and environmental factors that affect the long-term supply, transport, and fate of contaminants in the Nation’s streams. The SPARROW model relates in-stream water-quality data to spatially referenced characteristics of watersheds, including contaminant sources and factors influencing terrestrial and aquatic transport. Based on SPARROW modeling, one of the main nutrient sources to streams is point-source facilities such as municipal waste-water treatment plants that discharge directly to streams. This dataset was developed to assist with SPARROW models developed to assess supply, transport and fate of total nitrogen and phosphorous in streams of the conterminous United States (2012). This dataset documents discharge information from point sources in the conterminous United States and was obtained from the EPA Integrated Compliance Information System (ICIS) and Permit Compliance System (PCS). When available, nutrient concentrations were used to calculate point source loads. However, in many cases measured concentration data were not available in the ICIS or PCS data base and so “typical pollutant concentrations” (TPC’s) were developed using data from similar facilities. A new method for calculating TPC’s was implemented that allows varying amounts of nutrient concentration data and/or varying numbers of facilities to determine TPC’s. This dataset contains the EPA facility, flow, and concentration data and all updates to the data, along with the TPC tables and resultant total nitrogen and phosphorous loads calculated from the input datasets.