This data release contains estimated monthly point-source nutrient loads for 97 municipal wastewater treatment plants, 20 industrial facilities, and 46 fish hatcheries and other aquaculture facilities that discharge within the watersheds draining to Puget Sound and the Strait of Juan de Fuca in Washington, or discharge directly to those water bodies. The data, which cover the years 2005 through 2020, were used as input to a set of seasonal SPARROW total nitrogen and total phosphorus SPARROW models that were used to assess nutrient loadings to Puget Sound.

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.

This data release contains monthly deposition estimates of wet and total inorganic nitrogen (reduced and oxidized) for watersheds draining to the Puget Sound and the Strait of Juan de Fuca, Washington. The data, which cover the years 2005 through 2020, were used as input to a seasonal Spatially Referenced Regression On Watershed attributes (SPARROW) total nitrogen model that was used to assess nutrient loadings to Puget Sound and the Strait of Juan de Fuca. The values constitute the monthly nitrogen deposition for each incremental catchment represented in the SPARROW models.

This data release contains the watershed ancillary data that were used as input for a set of dynamic Spatially Referenced Regression On Watershed attributes (SPARROW) models for watersheds draining to Puget Sound and the Strait of Juan de Fuca, Washington for the years 2005 - 2020. The SPARROW models were used to estimate mean seasonal total nitrogen and total phosphorous conditions and the delivery of those nutrients to Puget Sound and the Strait of Juan de Fuca. The data sets in each child item, which consists of a collection of CSV files, represents landscape conditions in the incremental catchments that made up the hydrologic network used in the SPARROW modeling. The conditions for catchments that were partially or fully outside the domain of the original landscape data were estimated by extrapolating the conditions from nearby catchments.

This data release contains seasonal application estimates of nitrogen and phosphorus to cropland for watersheds draining to the Puget Sound and the Strait of Juan de Fuca, Washington. The data, which cover the years 2005 through 2020, were used as input to seasonal Spatially Referenced Regression On Watershed attributes (SPARROW) total nitrogen and total phosphorus models that were used to assess nutrient loadings to Puget Sound. The values constitute the seasonal nitrogen and phosphorus application for each incremental catchment represented in the SPARROW models.

This geospatial dataset depicts a sewage no-discharge zone established under Clean Water Act Section 312. The area(s) depicted are zones where the discharge of any sewage, treated or untreated, from vessels is prohibited. This layer was created using information from the corresponding Federal Register notice and is created for informational purposes, not to be used for enforcement.

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 data release contains measured streamflow data from U.S. Geological Survey (USGS) streamgages and reported wastewater data from wastewater treatment plants (WWTP) discharge monitoring reports (DMRs) within the Potomac River watershed between October 1, 2021 and September 30, 2024. Mean monthly streamflow data was obtained from 117 USGS streamgages (Table1_Streamgages.csv). Average monthly reported wastewater discharge volumes to surface water were obtained from National Pollutant Discharge Elimination System (NPDES) permits using the United States Environmental Protection Agency’s (USEPA) Environment and Compliance History Online (ECHO) database to obtain DMRs from the Integrated Compliance Information System National Pollutant Discharge Elimination System (ICIS-NPDES). Quality assurance procedures that were used to avoid inclusion of inaccurate data that can be reported on DMRs (Table2_WWTP_DMRs.csv) are documented within the Process Step fields of the metadata. At each streamgage the average monthly accumulated wastewater percentage (ACCWW) was calculated by dividing the total amount of reported wastewater upstream of the streamgage by the measured amount of streamflow (Table3_Streamgage_ACCWW.csv) following similar methods described in Miller and others (2024) and Barber and others (2025). The ACCWW calculations were computed monthly at each streamgage using reported total wastewater discharge, municipal wastewater discharge, and municipal-plus-industrial per- and polyfluoroalkyl substances (PFAS) wastewater discharge which includes municipal wastewater in addition to wastewater from industrial WWTPs that are potential PFAS handling industry sectors defined by the USEPA (2023). The term ‘municipal’ is used here to represent NPDES-permitted facilities with the Standard Industrial Classification code 4952 (‘sewerage systems’) and 'industrial' refers to permitted facilities with Standard Industrial Classification codes other than 4952. Monthly predicted environmental concentrations and constituent loads (i.e. mass fluxes) of eight PFAS and 14 pesticides were estimated at each streamgage following methodology presented by Barber and others (2025) and Miller and others (2024). Monthly PFAS loads were computed by multiplying the discharge volumes from municipal and industrial WWTPs that are potential PFAS handling industry sectors by the median PFAS concentrations measured and reported in Barber and others (2025). Monthly pesticide loads were computed by multiplying the discharge volumes from municipal WWTPs by the median pesticide concentrations reported in Miller and others (2024). Wastewater effluent concentrations from Miller and others (2024) and Barber and others (2025) are provided in Table4_Parameters.csv. Monthly predicted constituent loads from wastewater were summed from WWTPs that discharged to every National Hydrography Dataset Version 2.1 (NHDPlus V2; USEPA, 2012) stream segment Common Identifier (COMID) upstream of each streamgage, not including the COMID where the streamgage was located, to calculate the predicted monthly load at each streamgage (Table5_Streamgage_Parameter_Predictions.csv). Predicted monthly concentrations from wastewater were calculated by dividing the predicted monthly load by measured monthly streamflow at each streamgage (Table5_Streamgage_Parameter_Predictions.csv).