Data are from 1,000 river and stream sites across the conterminous US where consistent biological, chemical, physical and watershed data were gathered. The sites were selected using a probability survey design so that the results provide inferences to all perennial flowing waters in the lower 48 states. This dataset is associated with the following publication: Omernik, J., S. Paulsen , M. Weber , and G. Griffith. Regional patterns of total nitrogen concentrations in the National Rivers and Streams Assessment. JOURNAL OF SOIL AND WATER CONSERVATION. Soil and Water Conservation Society, 71(3): 167-181, (2016).

A digital representation of the watersheds of 43 sites on large river systems sampled by the National Stream Quality Accounting Network (NASQAN) of the U. S. Geological Survey (USGS) in 2000 was created primarily from 1:250,000 hydrologic units(HUCs) in the United States. Watershed information from Canada and Mexico was incorporated to complete the areas draining to the sampling sites from outside the United States. The sampled rivers are in one of four major river systems: the Mississippi, the Colorado, the Rio Grande, or the Columbia.

A digital representation of the watersheds of 43 sites on large river systems sampled by the National Stream Quality Accounting Network (NASQAN) of the U. S. Geological Survey (USGS) in 2000 was created primarily from 1:250,000 hydrologic units(HUCs) in the United States. Watershed information from Canada and Mexico was incorporated to complete the areas draining to the sampling sites from outside the United States. The sampled rivers are in one of four major river systems: the Mississippi, the Colorado, the Rio Grande, or the Columbia.

This is a combined dataset that includes data for 1966 of the 2008-2009 National Rivers and Streams Assessment watersheds. The data includes watershed N inputs and stream TN, TON and DIN concentrations. This dataset is associated with the following publication: Bellmore, R., J. Compton, R. Brooks, E. Fox, R. Hill, D. Sobota, D. Thornbrugh, and M. Weber. Nitrogen inputs drive nitrogen concentrations in U.S. streams and rivers during summer low flow conditions. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, NETHERLANDS, 639: 1349-1359, (2018).

This is a combined dataset that includes data for 1966 of the 2008-2009 National Rivers and Streams Assessment watersheds. The data includes watershed N inputs and stream TN, TON and DIN concentrations. This dataset is associated with the following publication: Bellmore, R., J. Compton, R. Brooks, E. Fox, R. Hill, D. Sobota, D. Thornbrugh, and M. Weber. Nitrogen inputs drive nitrogen concentrations in U.S. streams and rivers during summer low flow conditions. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, NETHERLANDS, 639: 1349-1359, (2018).

NRSA siteinfo, water chemistry, and physical habitat datasets from 2008-9, 2013-14, and 2018-19, StreamCat for wetland variables for each site. This dataset is associated with the following publication: Flotemersch, J., K. Blocksom, A. Herlihy, P. Kaufmann, R. Mitchell, and D. Peck. Distribution and Characteristics of Blackwater Rivers and Streams of the Contiguous United States. WATER RESOURCES RESEARCH. American Geophysical Union, Washington, DC, USA, 60(2): e2023WR035529, (2024).

In 1991, the U.S. Geological Survey (USGS) began a study of more than 50 major river basins across the Nation as part of the National Water-Quality Assessment (NAWQA) project of the National Water-Quality Program. One of the major goals of the NAWQA project is to determine how water-quality conditions change over time. To support that goal, long-term consistent and comparable monitoring has been conducted on streams and rivers throughout the Nation. Outside of the NAWQA project, the USGS and other Federal, State, and local agencies also have collected long-term water-quality data to support their own assessments of changing water-quality conditions. Data from these multiple sources have been combined to support one of the most comprehensive assessments conducted to date of water-quality trends in the United States. Ultimately, these data will provide insight into how natural features and human activities have contributed to water-quality changes over time in Nation’s streams and rivers. This USGS data release contains all of the input and output files necessary to reproduce the results of the Seasonal Kendall trend tests described in the associated U.S. Geological Survey Scientific Investigations Report (http://dx.doi.org/10.3133/sir20175006). Data preparation for input to the model is also fully described in the above-mentioned report.

In 1991, the U.S. Geological Survey (USGS) began a study of more than 50 major river basins across the Nation as part of the National Water-Quality Assessment (NAWQA) project of the National Water-Quality Program. One of the major goals of the NAWQA project is to determine how water-quality conditions change over time. To support that goal, long-term consistent and comparable monitoring has been conducted on streams and rivers throughout the Nation. Outside of the NAWQA project, the USGS and other Federal, State, and local agencies also have collected long-term water-quality data to support their own assessments of changing water-quality conditions. Data from these multiple sources have been combined to support one of the most comprehensive assessments conducted to date of water-quality trends in the United States. Ultimately, these data will provide insight into how natural features and human activities have contributed to water-quality changes over time in Nation’s streams and rivers. This USGS data release contains all of the input and output files necessary to reproduce the results of the Seasonal Kendall trend tests described in the associated U.S. Geological Survey Scientific Investigations Report. Data preparation for input to the model is also fully described in the above-mentioned report.

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/).

This dataset represents estimated surface water TN flux within individual, local NHDPlusV2 catchments and upstream, contributing watersheds. Measured as kg N/km2.