This data release contains a boosted regression tree (BRT) model (written in the R programming language), and the input and output data from that model that were used to relate base flow nitrate concentrations in the Chesapeake Bay watershed to catchment characteristics. The input data consists of two types of information: 1) surface water nitrate concentrations collected by the USGS and partnering agencies in the Chesapeake Bay watershed between 1970 and 2013 and 2) potential predictor variables that included nitrogen sources, catchment characteristics, soil and groundwater chemistry, soil drainage and composition, and aquifer geology. The results from the BRT model were used to identify ten significant predictors of base flow nitrate concentrations in streams in the Chesapeake Bay watershed.

The core equations of the SPARROW model (Schwarz and others, 2006) were implemented in differential form using the R programming language (R Core Team, 2017), as the basis of a tool for empirically relating a regional pattern of changes in constituent flux, over a multi-year period, to spatially referenced changes in explanatory variables over the same period. A pilot implementation was developed to explore factors influencing changes in flow-normalized flux of total nitrogen (TN) over the period 1990-2010 at 43 sites in the non-tidal Chesapeake Bay watershed. Model inputs, outputs, and code are included in this data release, and are described below.

The core equations of the SPARROW model (Schwarz and others, 2006) were implemented in differential form using the R programming language (R Core Team, 2017), as the basis of a tool for empirically relating a regional pattern of changes in constituent flux, over a multi-year period, to spatially referenced changes in explanatory variables over the same period. A pilot implementation was developed to explore factors influencing changes in flow-normalized flux of total nitrogen (TN) over the period 1990-2010 at 43 sites in the non-tidal Chesapeake Bay watershed. Model inputs, outputs, and code are included in this data release, and are described below.

The CBTN_v5 and CBTP_v5 SPARROW models were developed to support inferences about causes of observed changes in nitrogen and phosphorus (respectively) fluxes in Chesapeake Bay tributaries between 1992 and 2012. Model inputs and outputs are included in three files, which are described below. Detailed documentation of the SPARROW modeling technique is available at https://pubs.er.usgs.gov/publication/tm6B3.

The CBTN_v5 and CBTP_v5 SPARROW models were developed to support inferences about causes of observed changes in nitrogen and phosphorus (respectively) fluxes in Chesapeake Bay tributaries between 1992 and 2012. Model inputs and outputs are included in three files, which are described below. Detailed documentation of the SPARROW modeling technique is available at https://pubs.er.usgs.gov/publication/tm6B3.

This data release supports an analysis of changes in dissolved organic carbon (DOC) and nitrate concentrations in Buck Creek watershed near Inlet, New York 2001 to 2021. The Buck Creek watershed is a 310-hectare forested watershed that is recovering from acidic deposition within the Adirondack region. The data release includes pre-processed model inputs and model outputs for the Weighted Regressions on Time, Discharge and Season (WRTDS) model (Hirsch and others, 2010) to estimate daily flow normalized concentrations of DOC and nitrate during a 20-year period of analysis. WRTDS uses daily discharge and concentration observations implemented through the Exploration and Graphics for River Trends R package (EGRET) to predict solute concentration using decimal time and discharge as explanatory variables (Hirsch and De Cicco, 2015; Hirsch and others, 2010). Discharge and concentration data are available from the U.S. Geological Survey National Water Information System (NWIS) database (U.S. Geological Survey, 2016). The time series data were analyzed for the entire period, water years 2001 (WY2001) to WY2021 where WY2001 is the period from October 1, 2000 to September 30, 2001. This data release contains 5 comma-separated values (CSV) files, one R script, and one XML metadata file. There are four input files (“Daily.csv”, “INFO.csv”, “Sample_doc.csv”, and “Sample_nitrate.csv”) that contain site information, daily mean discharge, and mean daily DOC or nitrate concentrations. The R script (“Buck Creek WRTDS R script.R”) uses the four input datasets and functions from the EGRET R package to generate estimations of flow normalized concentrations. The output file (“WRTDS_results.csv”) contains model output at daily time steps for each sub-watershed and for each solute. Files are automatically associated with the R script when opened in RStudio using the provided R project file ("Files.Rproj"). All input, output, and R files are in the "Files.zip" folder.

This data release supports an analysis of changes in dissolved organic carbon (DOC) and nitrate concentrations in Buck Creek watershed near Inlet, New York 2001 to 2021. The Buck Creek watershed is a 310-hectare forested watershed that is recovering from acidic deposition within the Adirondack region. The data release includes pre-processed model inputs and model outputs for the Weighted Regressions on Time, Discharge and Season (WRTDS) model (Hirsch and others, 2010) to estimate daily flow normalized concentrations of DOC and nitrate during a 20-year period of analysis. WRTDS uses daily discharge and concentration observations implemented through the Exploration and Graphics for River Trends R package (EGRET) to predict solute concentration using decimal time and discharge as explanatory variables (Hirsch and De Cicco, 2015; Hirsch and others, 2010). Discharge and concentration data are available from the U.S. Geological Survey National Water Information System (NWIS) database (U.S. Geological Survey, 2016). The time series data were analyzed for the entire period, water years 2001 (WY2001) to WY2021 where WY2001 is the period from October 1, 2000 to September 30, 2001. This data release contains 5 comma-separated values (CSV) files, one R script, and one XML metadata file. There are four input files (“Daily.csv”, “INFO.csv”, “Sample_doc.csv”, and “Sample_nitrate.csv”) that contain site information, daily mean discharge, and mean daily DOC or nitrate concentrations. The R script (“Buck Creek WRTDS R script.R”) uses the four input datasets and functions from the EGRET R package to generate estimations of flow normalized concentrations. The output file (“WRTDS_results.csv”) contains model output at daily time steps for each sub-watershed and for each solute. Files are automatically associated with the R script when opened in RStudio using the provided R project file ("Files.Rproj"). All input, output, and R files are in the "Files.zip" folder.

This USGS data release contains datasets, metadata, and figures associated with estimating nitrate loads and yields from groundwater to streams in the Chesapeake Bay watershed based on land use and geology. There are three shapefiles with associated metadata and figures representing the shapefiles: • Catchments_GWcontribN.shp: NHDPlus catchment estimates of groundwater contribution of nitrate to streams in the Chesapeake Bay watershed • HUC12_GWcontribN.shp: HUC 12 estimates of groundwater contribution of nitrate to streams in the Chesapeake Bay watershed • Sites_GWcontribN.shp: Sites with baseflow measurements for nitrate plus nitrite within the Chesapeake Bay watershed These data support the following publication: • Terziotti, Silvia, Capel, P.D., Tesoriero, A.J., Hopple, J.A., and Kronholm, S.C., 2017, Estimates of nitrate loads and yields from groundwater to streams in the Chesapeake Bay watershed based on land use and geology: U.S. Geological Survey Scientific Investigations Report 2017-5160, 20 p., https://doi.org/10.3133/sir20175160.

This USGS data release contains datasets, metadata, and figures associated with estimating nitrate loads and yields from groundwater to streams in the Chesapeake Bay watershed based on land use and geology. There are three shapefiles with associated metadata and figures representing the shapefiles: • Catchments_GWcontribN.shp: NHDPlus catchment estimates of groundwater contribution of nitrate to streams in the Chesapeake Bay watershed • HUC12_GWcontribN.shp: HUC 12 estimates of groundwater contribution of nitrate to streams in the Chesapeake Bay watershed • Sites_GWcontribN.shp: Sites with baseflow measurements for nitrate plus nitrite within the Chesapeake Bay watershed These data support the following publication: • Terziotti, Silvia, Capel, P.D., Tesoriero, A.J., Hopple, J.A., and Kronholm, S.C., 2017, Estimates of nitrate loads and yields from groundwater to streams in the Chesapeake Bay watershed based on land use and geology: U.S. Geological Survey Scientific Investigations Report 2017-5160, 20 p., https://doi.org/10.3133/sir20175160.

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.