This product consists of a table of annual discharge estimates in millions of gallons per day from wastewater treatment plants (WWTPs) for 1,518 watersheds in the conterminous United States. The data are based on information extracted from the U.S. Environmental Protection Agency’s Clean Watersheds Needs Survey. The data are for 13 time periods, beginning in 1978 and ending in 2012. Total nitrogen and phosphorus loads from WWTPs per watershed for each year are also provided, based on previously published data (Falcone, 2017).

This spatial data set was created by the U.S. Geological Survey (USGS) to represent the amount of total nitrogen and total phosphorus discharged to surface waters in the Pacific Northwest region of the United States (Hydro Region 17; Major River Basin 7 (MRB7)) during 2002 from individual permitted wastewater facilities.

This spatial data set was created by the U.S. Geological Survey (USGS) to represent the amount of total nitrogen and total phosphorus discharged to surface waters in the Pacific Northwest region of the United States (Hydro Region 17; Major River Basin 7 (MRB7)) during 2002 from individual permitted wastewater facilities.

This spatial data set was created by the U.S. Geological Survey (USGS) to represent the amount of total nitrogen and total phosphorus discharged to surface waters in the Pacific Northwest region of the United States (Hydro Region 17; Major River Basin 7 (MRB7)) during 2002 from all permitted wastewater facilities located within each incremental watershed delineated in the NHDPlus v2 dataset.

This dataset contains tabular data for U.S. Environmental Protection Agency’s (EPA) Clean Watersheds Needs Survey (CWNS) wastewater treatment facility information. Literature-based average total nitrogen and total phosphorous concentrations were substituted for wastewater treatment levels reported for each facility because little or no concentration data is reported in the CWNS. Concentrations were based on the treatment levels of raw, primary, secondary, and advanced. Concentration and effluent flow-value data gaps were ‘filled in’ through simple linear assumptions, based on each facility’s responses to the survey in years bracketing the data gap or were based on an un-bracketed single year survey response. Unlike the McMahon and others (2007) method used to complete the EPA Permit Compliance System/Integrated Compliance Information System (PCS/ICIS) dataset where data from similar facilities was used to fill the data gaps, treatment level and flow data unique to each facility were used to complete the Clean Watershed Needs Survey dataset. [McMahon, Gerard, Tervelt, Larinda, and Donehoo, William, 2007, Methods for estimating annual wastewater nutrient loads in the southeastern United States: U.S. Geological Survey Open-File Report 2007-1040, 81 p., https://pubs.usgs.gov/of/2007/1040/] The Clean Watershed Needs Survey data were collected by the EPA for the years 1978, 1980, 1982, 1984, 1986, 1988, 1990, 1992, 1996, 2000, 2004, 2008 and 2012, and total nitrogen and total phosphorous loads were calculated using reported annual flows and nutrient concentration values substituted from literature for reported treatment levels from the CWNS. The long-term nutrient loads are provided as supportive information for studies being conducted by the USGS National Water Quality Assessment (NAWQA) Project.

This dataset contains tabular data for U.S. Environmental Protection Agency’s (EPA) Clean Watersheds Needs Survey (CWNS) wastewater treatment facility information. Literature-based average total nitrogen and total phosphorous concentrations were substituted for wastewater treatment levels reported for each facility because little or no concentration data is reported in the CWNS. Concentrations were based on the treatment levels of raw, primary, secondary, and advanced. Concentration and effluent flow-value data gaps were ‘filled in’ through simple linear assumptions, based on each facility’s responses to the survey in years bracketing the data gap or were based on an un-bracketed single year survey response. Unlike the McMahon and others (2007) method used to complete the EPA Permit Compliance System/Integrated Compliance Information System (PCS/ICIS) dataset where data from similar facilities was used to fill the data gaps, treatment level and flow data unique to each facility were used to complete the Clean Watershed Needs Survey dataset. [McMahon, Gerard, Tervelt, Larinda, and Donehoo, William, 2007, Methods for estimating annual wastewater nutrient loads in the southeastern United States: U.S. Geological Survey Open-File Report 2007-1040, 81 p., https://pubs.usgs.gov/of/2007/1040/] The Clean Watershed Needs Survey data were collected by the EPA for the years 1978, 1980, 1982, 1984, 1986, 1988, 1990, 1992, 1996, 2000, 2004, 2008 and 2012, and total nitrogen and total phosphorous loads were calculated using reported annual flows and nutrient concentration values substituted from literature for reported treatment levels from the CWNS. The long-term nutrient loads are provided as supportive information for studies being conducted by the USGS National Water Quality Assessment (NAWQA) Project.

The U.S. Geological Survey (USGS) is developing SPARROW models (SPAtially Related Regressions On Watershed Attributes) to assess the transport of contaminants (for example, nutrients) through the Pacific drainages of the United States (the Columbia River basin; the coastal drainages of Washington, Oregon, and California; the Klamath River basin; the Central Valley of California, and the west slopes of the Sierra Nevada Mountains). SPARROW relates instream water quality measurements to spatially referenced characteristics of watersheds, including contaminant sources and the factors influencing terrestrial and aquatic transport. The number of people with on-site wastewater treatment (primarily septic tanks) is a potential factor affecting nutrient delivery to streams. The spatial data set “Population with On-Site Wastewater Treatment within the Pacific Drainages of the United States (2010)" represents the number of people that did not have access to centralized municipal wastewater treatment in 2010. This data set was created by disaggregating census block populations to developed land and retaining those populations that were outside of the service boundaries for municipal wastewater treatment plants.