This is a point coverage of stations in the U.S. Geological Survey's National Stream Quality Accounting Network (NASQAN). NASQAN was established in 1973. Water-quality data currently is collected at NASQAN sites on bimonthly and quarterly intervals. However, some of the bimonthly stations will be sampled only five times a year beginning in 1992. Separate coverages exist for the conterminous United States, Alaska, Hawaii/Guam, and Puerto Rico. The coverages attempt to represent all of the stations that are or have been in the network (some are inactive or discontinued) as of spring 1992. United States Water quality Surface water

This dataset and the accompanying Data Series report was created to assist in analysis and interpretation of water-quality data provided by the U.S. Geological Survey, National Stream Quality Accounting Network (NASQAN) and the National Monitoring Network (NMN). The report describes the methods used to develop the geospatial data which was primarily derived from the National Watershed Boundary Dataset (WBD12). The geospatial data contains polygon shapefiles of basin boundaries for 33 NASQAN and 5 NMN stations. In addition, 30 polygon shapefiles of the closed and noncontributing basins contained within the NASQAN or NMN boundaries where applicable are included. Also included is a point shapefile of the NASQAN and NMN gaging stations and associated basin and station attributes. The basin boundaries included in this dataset are for those sites implemented under the October 2007 design for the 5-years from 2008-2013 (http://water.usgs.gov/nasqan/).

From October 2017 through September 2022, the National Water Quality Network (NWQN) monitored 110 surface-water river and stream sites and more than 1,800 groundwater wells for a large number of water-quality analytes, for which associated quality-control data and corresponding statistical summaries are included in this data release. The quality-control data—for samples that were collected in the field (at all 110 surface-water sites, 350 groundwater wells, and 16 quality-control-only sites), prepared in the laboratory, or prepared by a third party—can be used to assess the quality of environmental data collected by the NWQN through the estimation of bias and variability in reported results. The general analyte groups that were monitored at NWQN surface-water and (or) groundwater sites and have associated quality-control data in this data release include major ions, nutrients, trace elements, pesticides, volatile organic compounds, hormones, pharmaceuticals, radionuclides, microbial indicators, sediment, and environmental tracers. For each analyte group, the data tables contain results for one or more of the following types of quality-control samples, where relevant: blanks, matrix spikes, and replicates collected at field sites; laboratory blanks, reagent spikes, and matrix spikes prepared by the USGS National Water Quality Laboratory (NWQL) (quality-control samples prepared by other analyzing laboratories are not included in the current data release); and third-party blanks, spikes, and reference samples prepared by the USGS Quality Systems Branch (QSB). For each relevant analyte, tables of summary statistics characterize the frequency and concentrations of blank detections, the typical magnitude of and variability in spike and reference-sample recoveries, and the typical variability between replicate concentrations. Tables included in this data release: Table1_SiteList.txt: Information about National Water Quality Network sites that have associated quality-control data. Table2_AnalyteList.txt: Information about National Water Quality Network analytes that have associated quality-control data, including available aquatic-life and (or) human-health benchmarks and selected information regarding analytical methods. Table3_BlankData.txt: For all relevant analytes, results for blanks collected at field sites, prepared in the laboratory, or prepared by a third party. Table4_SpikeData.txt: For all relevant analytes, results for matrix spikes prepared in the field, matrix spikes prepared in the laboratory, reagent spikes prepared in the laboratory, or reagent spikes prepared by a third party. For matrix spikes, results of paired environmental samples are included. Table5_ReplicateData.txt: For all relevant analytes, results for field replicates and paired environmental samples. Table 6_ReferenceData.txt: For all relevant analytes, results for third-party reference samples. Table7_BlankStats.txt: For all relevant analytes, summary statistics for each type of available blank sample. Table8_SpikeStats.txt: For all relevant analytes, summary statistics for each type of available spike sample. Table9_ReplicateStats.txt: For all relevant analytes, summary statistics for field replicates. Table10_ReferenceStats.txt: For all relevant analytes, summary statistics for reference samples.

This is a coverage of the boundaries and codes used for the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program Study-Unit investigations in the conterminous United States, excluding the High Plains Regional Ground-Water Study. The data set represents the areas to be studied during the second cycle of the NAWQA Program, from 2001-2012 ("cycle 2").

Groundwater-quality data were collected from 983 wells as part of the National Water-Quality Assessment Project of the U.S. Geological Survey National Water-Quality Program and are included in this report. The data were collected from six types of well networks: principal aquifer study networks, which are used to assess the quality of groundwater used for public water supply; land-use study networks, which are used to assess land-use effects on shallow groundwater quality; major aquifer study networks, which are used to assess the quality of groundwater used for domestic supply; enhanced trends networks, which are used to evaluate the time scales during which groundwater quality changes; vertical flow-path study networks, which are used to evaluate changes in groundwater quality from shallow to deeper depths; and modeling support studies, which are used to provide data to support groundwater modeling. Groundwater samples were analyzed for a large number of water-quality indicators and constituents, including major ions, nutrients, trace elements, volatile organic compounds, pesticides, radionuclides, microbiological indicators, and some special interest constituents (arsenic speciation, chromium [VI] and perchlorate). Most of the data included were collected from wells that were sampled between January 2017 and December 2019. Microbiological indicator data for networks sampled in 2016 are included in this data release. These groundwater quality networks are described in a U.S. Geological Survey Data Series report DS####, which is available at https://dx.doi.org/XXXXXX, and the results are in this data release. Data for quality-control samples collected in 2017 through 2019 also are included in this data release. Data from samples collected between 2012 and 2016 are associated with networks described in previous reports in this data series (Arnold and others, 2016a and b; 2017a and b; 2018a and b; and 2020a and b). There are 24 data tables included in this data release and they are referenced as tables 1 through 14 and appendix tables 5-11 through 5-20 in the larger work citation (see supplemental information for descriptions). Two tables summarizing well depth and open interval are included in the data series report and were derived from table 1 in this data release. A separate table named DSR_2017-19_Description_of_Data_Fields.txt describes the 405 unique fields contained in the 24 data tables.

The National Water Quality Network (NWQN) for Rivers and Streams includes 113 surface-water river and stream sites monitored by the U.S. Geological Survey (USGS) National Water Quality Program (NWQP). The NWQN represents the consolidation of four historical national networks: the USGS National Water-Quality Assessment (NAWQA) Project, the USGS National Stream Quality Accounting Network (NASQAN), the National Monitoring Network (NMN), and the Hydrologic Benchmark Network (HBN). The NWQN includes 22 large river coastal sites, 41 large river inland sites, 30 wadeable stream reference sites, 10 wadeable stream urban sites, and 10 wadeable stream agricultural sites. In addition to the 113 NWQN sites, 3 large inland river monitoring sites from the USGS Cooperative Matching Funds (Co-op) program are also included in this annual water-quality reporting Web site to be consistent with previous USGS studies of nutrient transport in the Mississippi-Atchafalaya River Basin. This data release contains geo-referenced digital data and associated attributes of watershed boundaries for 113 NWQN and 3 Co-op sites. Two sites, "Wax Lake Outlet at Calumet, LA"; 07381590, and "Lower Atchafalaya River at Morgan City, LA"; 07381600, are outflow distributaries into the Gulf of Mexico. Watershed boundaries were delineated for the portion of the watersheds between "Red River near Alexandria, LA"; 07355500 and "Atchafalaya River at Melville, LA"; 07381495 to the two distributary sites respectively. Drainage area was undetermined for these two distributary sites because the main stream channel outflows into many smaller channels so that streamflow is no longer relative to the watershed area. NWQN watershed boundaries were derived from the Watershed Boundary Dataset-12-digit hydrologic units (WBD-12). The development of the WBD-12 was a coordinated effort between the United States Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS), the USGS, and the Environmental Protection Agency (EPA) (U.S. Department of Agriculture-Natural Resources Conservation Service, 2012). A hydrologic unit is a drainage area delineated to nest in a multi-level, hierarchical drainage system. Its boundaries are defined by hydrographic and topographic criteria that delineate an area of land upstream from a specific point on a river, stream or similar surface waters. The United States is divided and sub-divided into successively smaller hydrologic units identified by a unique hydrologic unit code (HUC) consisting of two to 12 digits based on the six levels of classification in the hydrologic unit system: regions, sub-regions, accounting units, cataloging units, watersheds, and sub-watersheds. NWQN watershed boundaries were delineated by selecting all sub-watershed polygons that flow into the most downstream WBD-12 polygon in which the NWQN site is located. The WBD-12 attribute table contains 8-digit, 10-digit, and 12-digit HUCs which were used to identify which sub-watersheds flow into the watershed pour point at the NWQN site location. When the NWQN site was located above the pour point of the most downstream sub-watershed, the sub-watershed was edited to make the NWQN site the pour point of that sub-watershed. To aid editing, USGS 1:24,000 digital topographic maps were used to determine the hydrologic divide from the sub-watershed boundary to the NWQN pour point. The number of sub-watersheds which are contained within the NWQN watersheds ranged from less than one to nearly 32,000 internal sub-watersheds. Internal sub-watershed boundaries were dissolved so that a single watershed boundary was generated for each NWQN watershed. Data from this release are presented at the USGS Tracking Water Quality page: http://cida.usgs.gov/quality/rivers/home (Deacon and others, 2015). Watershed boundaries delineated for this release do not take into account non-contributing area, diversions out of the watershed, or return flows into the watershed. Delineations are based

The National Water Quality Network (NWQN) for Rivers and Streams includes 113 surface-water river and stream sites monitored by the U.S. Geological Survey (USGS) National Water Quality Program (NWQP). The NWQN represents the consolidation of four historical national networks: the USGS National Water-Quality Assessment (NAWQA) Project, the USGS National Stream Quality Accounting Network (NASQAN), the National Monitoring Network (NMN), and the Hydrologic Benchmark Network (HBN). The NWQN includes 22 large river coastal sites, 41 large river inland sites, 30 wadeable stream reference sites, 10 wadeable stream urban sites, and 10 wadeable stream agricultural sites. In addition to the 113 NWQN sites, 3 large inland river monitoring sites from the USGS Cooperative Matching Funds (Co-op) program are also included in this annual water-quality reporting Web site to be consistent with previous USGS studies of nutrient transport in the Mississippi-Atchafalaya River Basin. This data release contains geo-referenced digital data and associated attributes of watershed boundaries for 113 NWQN and 3 Co-op sites. Two sites, "Wax Lake Outlet at Calumet, LA"; 07381590, and "Lower Atchafalaya River at Morgan City, LA"; 07381600, are outflow distributaries into the Gulf of Mexico. Watershed boundaries were delineated for the portion of the watersheds between "Red River near Alexandria, LA"; 07355500 and "Atchafalaya River at Melville, LA"; 07381495 to the two distributary sites respectively. Drainage area was undetermined for these two distributary sites because the main stream channel outflows into many smaller channels so that streamflow is no longer relative to the watershed area. NWQN watershed boundaries were derived from the Watershed Boundary Dataset-12-digit hydrologic units (WBD-12). The development of the WBD-12 was a coordinated effort between the United States Department of Agriculture-Natural Resources Conservation Service (USDA-NRCS), the USGS, and the Environmental Protection Agency (EPA) (U.S. Department of Agriculture-Natural Resources Conservation Service, 2012). A hydrologic unit is a drainage area delineated to nest in a multi-level, hierarchical drainage system. Its boundaries are defined by hydrographic and topographic criteria that delineate an area of land upstream from a specific point on a river, stream or similar surface waters. The United States is divided and sub-divided into successively smaller hydrologic units identified by a unique hydrologic unit code (HUC) consisting of two to 12 digits based on the six levels of classification in the hydrologic unit system: regions, sub-regions, accounting units, cataloging units, watersheds, and sub-watersheds. NWQN watershed boundaries were delineated by selecting all sub-watershed polygons that flow into the most downstream WBD-12 polygon in which the NWQN site is located. The WBD-12 attribute table contains 8-digit, 10-digit, and 12-digit HUCs which were used to identify which sub-watersheds flow into the watershed pour point at the NWQN site location. When the NWQN site was located above the pour point of the most downstream sub-watershed, the sub-watershed was edited to make the NWQN site the pour point of that sub-watershed. To aid editing, USGS 1:24,000 digital topographic maps were used to determine the hydrologic divide from the sub-watershed boundary to the NWQN pour point. The number of sub-watersheds which are contained within the NWQN watersheds ranged from less than one to nearly 32,000 internal sub-watersheds. Internal sub-watershed boundaries were dissolved so that a single watershed boundary was generated for each NWQN watershed. Data from this release are presented at the USGS Tracking Water Quality page: http://cida.usgs.gov/quality/rivers/home (Deacon and others, 2015). Watershed boundaries delineated for this release do not take into account non-contributing area, diversions out of the watershed, or return flows into the watershed. Delineations are based

This is a GENERALIZED version of the boundaries and codes used for the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program Study-Unit investigations in the conterminous United States, excluding the High Plains Regional Ground-Water Study. The data set represents the areas studied during the first decade of the NAWQA Program, from 1991-2001 ("cycle 1"). The coverage is intended only for drawing ILLUSTRATIONS, NOT for spatial analysis. The sources of this coverage were the full resolution NAWQA study unit coverage, which is available at https://water.usgs.gov/lookup/getspatial?nawqacyc1 and the coastline from a 1:2 million county coverage generalized for display at the scale of 1:34 million.

This is a GENERALIZED version of the boundaries and codes used for the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program Study-Unit investigations in the conterminous United States, excluding the High Plains Regional Ground-Water Study. The data set represents the areas studied during the first decade of the NAWQA Program, from 1991-2001 ("cycle 1"). The coverage is intended only for drawing ILLUSTRATIONS, NOT for spatial analysis. The sources of this coverage were the full resolution NAWQA study unit coverage, which is available at https://water.usgs.gov/lookup/getspatial?nawqacyc1 and the coastline from a 1:2 million county coverage generalized for display at the scale of 1:34 million.

This is a GENERALIZED version of the boundaries and codes used for the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program Study-Unit investigations in the conterminous United States, excluding the High Plains Regional Ground-Water Study. The data set represents the areas to be studied during the second decade of the NAWQA Program, from 2001-2012 ("cycle 2"). The coverage is intended only for drawing ILLUSTRATIONS, NOT for spatial analysis.