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 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.

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 estimated seasonal total nitrogen (TN) and total phosphorus (TP) loads during 2005 through 2020 in selected streams of the watersheds draining to Washington waters of the Salish Sea (Puget Sound region). Two load estimation methods were used: Fluxmaster (Schwarz and others, 2006, https://doi.org/10.3133/tm6B3) and Weighted Regression on Time, Discharge, and Season (WRTDS) with Kalman filtering (Hirsch and De Cicco, 2015, https://doi.org/10.1016/j.envsoft.2015.07.017). Together with the water-quality data, streamflow data, and estimated nitrogen and phosphorus loads, this release also provides copies of computer programming script that can be used to recreate the load estimates or modified for similar applications (see Process Steps). Seasonal TN and TP loads paired with streamflow were estimated at 50 locations. For convenience, seasonal summaries are also provided of observed streamflow at 128 locations and of observed water temperature at 29 locations.

This data release contains estimated seasonal total nitrogen (TN) and total phosphorus (TP) loads during 2005 through 2020 in selected streams of the watersheds draining to Washington waters of the Salish Sea (Puget Sound region). Two load estimation methods were used: Fluxmaster (Schwarz and others, 2006, https://doi.org/10.3133/tm6B3) and Weighted Regression on Time, Discharge, and Season (WRTDS) with Kalman filtering (Hirsch and De Cicco, 2015, https://doi.org/10.1016/j.envsoft.2015.07.017). Together with the water-quality data, streamflow data, and estimated nitrogen and phosphorus loads, this release also provides copies of computer programming script that can be used to recreate the load estimates or modified for similar applications (see Process Steps). Seasonal TN and TP loads paired with streamflow were estimated at 50 locations. For convenience, seasonal summaries are also provided of observed streamflow at 128 locations and of observed water temperature at 29 locations.

During the spring and summer of 2022, the U.S. Geological Survey collected water-quality samples for nutrient analysis at 45 stations across the state of Connecticut and adjacent areas of New York and Rhode Island to better understand the groundwater discharge component of nitrogen loading to the Long Island Sound. The targeted stations were located in small drainage basins (less than 50 square kilometers) in the southern portion of the Long Island Sound watershed. Sites were selected randomly from groups based on expected drivers or controls on baseflow nitrogen loads. Factors used in the grouping included four metrics calculated for the upstream watershed: percent impervious cover, septic system density, percent agricultural or turf grass land cover, and percent coarse-grained stratified sediments. The water-quality samples and instantaneous discharge measurements were collected under baseflow conditions during two separate synoptic sampling events, one in the nongrowing season (April 2022) and one in the growing season (June and July 2022). Instantaneous discharge measurements were collected in addition to water-quality samples to enable the calculations of nitrogen loads and yields. The water-quality samples were analyzed for physical properties and concentrations of chloride, nutrient species, and dissolved organic carbon; some analyses were performed past analytical method holding times. This data release includes site characteristics and geospatial data for potential and final (selected) sites, as well as field data, analytical results, and calculated nitrogen loads and yields for the final sites. Column names, units and descriptions are provided in data_dictionary.txt and a lookup table for method codes is provided in MethodLookupTable.txt. Note that many station identifiers (site_no) have a leading "0" that should be retained.

During the spring and summer of 2022, the U.S. Geological Survey collected water-quality samples for nutrient analysis at 45 stations across the state of Connecticut and adjacent areas of New York and Rhode Island to better understand the groundwater discharge component of nitrogen loading to the Long Island Sound. The targeted stations were located in small drainage basins (less than 50 square kilometers) in the southern portion of the Long Island Sound watershed. Sites were selected randomly from groups based on expected drivers or controls on baseflow nitrogen loads. Factors used in the grouping included four metrics calculated for the upstream watershed: percent impervious cover, septic system density, percent agricultural or turf grass land cover, and percent coarse-grained stratified sediments. The water-quality samples and instantaneous discharge measurements were collected under baseflow conditions during two separate synoptic sampling events, one in the nongrowing season (April 2022) and one in the growing season (June and July 2022). Instantaneous discharge measurements were collected in addition to water-quality samples to enable the calculations of nitrogen loads and yields. The water-quality samples were analyzed for physical properties and concentrations of chloride, nutrient species, and dissolved organic carbon; some analyses were performed past analytical method holding times. This data release includes site characteristics and geospatial data for potential and final (selected) sites, as well as field data, analytical results, and calculated nitrogen loads and yields for the final sites. Column names, units and descriptions are provided in data_dictionary.txt and a lookup table for method codes is provided in MethodLookupTable.txt. Note that many station identifiers (site_no) have a leading "0" that should be retained.

This U.S. Geological Survey (USGS) data release presents tabular data on nitrogen concentrations and loads for multiple nitrogen species, and river discharge data used in the analysis of data collected from October 1994 to September 2021. Data on flow and nitrogen concentrations were analyzed using the USGS Exploration and Graphics for RivEr Trends (EGRET) R package, and the method of Weighted Regression on Time Discharge and Season (WRTDS). Data and outputs summarized are for water-quality data collected from 17 water-quality monitoring stations in the Long Island Sound watershed. Specific data in tabular format for this release include: calculated annual nitrogen concentration and loads, calculated annual flow-normalized nitrogen concentrations and loads by water year (for sites with 20 years of data or more), and calculated annual seasonal loads of each nitrogen constituent by calendar year. Measured daily river discharge data and sampled nitrogen concentration data for each water-quality monitoring site are available as outputs accessible within R statistical software and as comma-separated values (CSV) files. This data release provides an update of data originally generated for use in nitrogen budget models for Long Island Sound (Vlahos and others, 2020), and the associated data release (Mullaney, 2020). Mullaney, J.R., 2020, Nitrogen concentrations and loads and seasonal nitrogen loads in selected Long Island Sound tributaries, water years 1995-2016: U.S. Geological Survey data release, https://doi.org/10.5066/P9AVXGBB. Vlahos, P., Whitney, M.M., Menniti, C., Mullaney, J.R., Morrison, J., Jia, Y., 2020, Nitrogen budgets of the Long Island Sound estuary: Estuarine, Coastal, and Shelf Science, v. 232, no 104693, https://doi.org/10.1016/j.ecss.2019.106493.

This U.S. Geological Survey data release presents tabular data on nitrogen concentrations and loads for multiple nitrogen species, and river discharge data used in the analysis of data collected from October 1994 to September 2016. Data on flow and nitrogen concentrations were analyzed using the USGS EGRET R package, and the method of WRTDS (Weighted Regression on Time Discharge and Season). Data and outputs summarized are for water-quality data collected from 18 water-quality monitoring stations in the Long Island Sound watershed. Specific data in tabular format for this release include: calculated annual nitrogen concentration and loads, calculated annual flow-normalized nitrogen concentrations and loads by water year (for sites with 20 years of data or more), and calculated annual seasonal loads of each nitrogen constituent by calendar year. Measured daily river discharge data and sampled nitrogen concentration data for each water-quality monitoring site are available as tables accessible within R statistical software.

This data release contains the number of households using on-site wastewater treatment for watersheds draining to the Puget Sound and the Strait of Juan de Fuca, Washington. The data, which represent the year 2010, 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 and the Strait of Juan de Fuca. The values constitute the total number of households using on-site wastewater treatment for each incremental catchment represented in the SPARROW models.