This data release contains drainage basin characteristics and low-streamflow trend results for 2,482 U.S. Geological Survey (USGS) streamgages in the conterminous U.S. Data include streamgage identification number, name, drainage area, latitude, longitude, percent developed land use, percent crop land use, dam storage, streamgage classification, record completeness status, and trend slopes and significance for several low-streamflow and related metrics. Also included is an R script containing the Mann-Kendall trend test for three different null hypotheses of the serial structure of the time-series data: independence, short-term persistence, and long-term persistence. Revised February 2019 (ver. 2.0)

This data release contains drainage basin characteristics and peak-streamflow trend and change-point results for 2,683 U.S. Geological Survey (USGS) streamgages in the conterminous U.S. Data include streamgage identification number, name, drainage area, latitude, longitude, percent urban land use, dam storage, streamgage classification, record completeness status, lag-1 autocorrelation, trend slopes and significance, peaks-over-threshold counts, trends in the numbers of peaks-over-threshold, and change point years and values for median and scale. Also included is an R script containing the Mann-Kendall trend test for three different null hypotheses of the serial structure of the time-series data: independence, short-term persistence, and long-term persistence. Revised - April 8, 2019 (ver. 3.0).

This data release contains drainage basin characteristics and peak-streamflow trend and change-point results for 2,683 U.S. Geological Survey (USGS) streamgages in the conterminous U.S. Data include streamgage identification number, name, drainage area, latitude, longitude, percent urban land use, dam storage, streamgage classification, record completeness status, lag-1 autocorrelation, trend slopes and significance, peaks-over-threshold counts, trends in the numbers of peaks-over-threshold, and change point years and values for median and scale. Also included is an R script containing the Mann-Kendall trend test for three different null hypotheses of the serial structure of the time-series data: independence, short-term persistence, and long-term persistence. Revised - April 8, 2019 (ver. 3.0).

Identifying long-term trends in water availability, including surface water quantity, is a key part of the U.S. Geological Survey (USGS) Integrated Water Availability Assessments (IWAAs) mission. This data release includes input and output data used in Mann-Kendall trend analyses to characterize streamflow conditions at 124 USGS streamgages in the Upper Colorado River Basin for water years 1982 through 2021. The Upper Colorado Riven Basin is defined here as the basin area upstream of USGS streamgage Colorado River above Lee's Ferry, AZ (USGS site number 09380000). Input data included annual (111 streamgages), seasonal (119 streamgages), and monthly (121 streamgages) streamflow metrics, calculated from daily mean streamflow data from the USGS National Water Information System (NWIS) database. Annual streamflow metrics include mean and median annual streamflow, 1-day, 7-day, and 30-day maximum annual streamflow; 1-day, 7-day, and 30-day minimum annual streamflow; and the date of the center of volume (the date on which 50 percent of the annual streamflow has passed by a streamgage). Seasonal metrics were calculated for Fall (October-December), Winter (January-March), Spring (April-June), and Summer (July-September) and include mean and median seasonal streamflow, 1-day and 7-day maximum seasonal streamflow, and 1-day and 7-day minimum seasonal streamflow. Monthly metrics include mean and median monthly streamflow, 1-day and 7-day maximum monthly streamflow, and 1-day and 7-day minimum monthly streamflow. Trend analyses using the Mann-Kendall test were completed on the annual, seasonal, and monthly metrics, which were passed through a series of data completeness filters to ensure robust trend analyses. Trend analyses were conducted for climate years 1982 through 2021 for low-flow metrics (where each climate year represents April – March), and trend analyses were conducted for water years 1982 through 2021 for all other metrics (where each water year represents October – September).

Identifying long-term trends in water availability, including surface water quantity, is a key part of the U.S. Geological Survey (USGS) Integrated Water Availability Assessments (IWAAs) mission. This data release includes input and output data used in Mann-Kendall trend analyses to characterize streamflow conditions at 124 USGS streamgages in the Upper Colorado River Basin for water years 1982 through 2021. The Upper Colorado Riven Basin is defined here as the basin area upstream of USGS streamgage Colorado River above Lee's Ferry, AZ (USGS site number 09380000). Input data included annual (111 streamgages), seasonal (119 streamgages), and monthly (121 streamgages) streamflow metrics, calculated from daily mean streamflow data from the USGS National Water Information System (NWIS) database. Annual streamflow metrics include mean and median annual streamflow, 1-day, 7-day, and 30-day maximum annual streamflow; 1-day, 7-day, and 30-day minimum annual streamflow; and the date of the center of volume (the date on which 50 percent of the annual streamflow has passed by a streamgage). Seasonal metrics were calculated for Fall (October-December), Winter (January-March), Spring (April-June), and Summer (July-September) and include mean and median seasonal streamflow, 1-day and 7-day maximum seasonal streamflow, and 1-day and 7-day minimum seasonal streamflow. Monthly metrics include mean and median monthly streamflow, 1-day and 7-day maximum monthly streamflow, and 1-day and 7-day minimum monthly streamflow. Trend analyses using the Mann-Kendall test were completed on the annual, seasonal, and monthly metrics, which were passed through a series of data completeness filters to ensure robust trend analyses. Trend analyses were conducted for climate years 1982 through 2021 for low-flow metrics (where each climate year represents April – March), and trend analyses were conducted for water years 1982 through 2021 for all other metrics (where each water year represents October – September).

The U.S. Geological Survey (USGS), in cooperation with the Wyoming Water Development Office, developed streamflow statistics for active (through September 30, 2021) and discontinued USGS streamgages in and near Wyoming with 10 or more years of daily mean streamflow record. The computation of streamflow statistics for USGS streamgages is part of a larger study to develop a StreamStats application (www.usgs.gov/streamstats) for the State of Wyoming (https://www.usgs.gov/centers/wyoming-montana-water-science-center/science/wyoming-streamstats). StreamStats is a web-based computer program that can be used to delineate drainage areas, determine basin characteristics, and compute streamflow statistics at locations with and without streamgages (https://streamstats.usgs.gov/ss/; Ries and others, 2024). Streamflow at each streamgage was assessed for degree of human alteration owing to dams and diversions before streamflow statistics were computed. Streamflow records from 631 streamgage periods of record were used to compute basic, seasonal, and flow-duration statistics; records for 390 streamgage periods of record were used to compute n-day statistics and statistics that can be used for regional regression. Methods used to compute the summary statistics contained in this data release are described in an accompanying report (Armstrong and others, 2025).

The U.S. Geological Survey (USGS), in cooperation with the Wyoming Water Development Office, developed streamflow statistics for active (through September 30, 2021) and discontinued USGS streamgages in and near Wyoming with 10 or more years of daily mean streamflow record. The computation of streamflow statistics for USGS streamgages is part of a larger study to develop a StreamStats application (www.usgs.gov/streamstats) for the State of Wyoming (https://www.usgs.gov/centers/wyoming-montana-water-science-center/science/wyoming-streamstats). StreamStats is a web-based computer program that can be used to delineate drainage areas, determine basin characteristics, and compute streamflow statistics at locations with and without streamgages (https://streamstats.usgs.gov/ss/; Ries and others, 2024). Streamflow at each streamgage was assessed for degree of human alteration owing to dams and diversions before streamflow statistics were computed. Streamflow records from 631 streamgage periods of record were used to compute basic, seasonal, and flow-duration statistics; records for 390 streamgage periods of record were used to compute n-day statistics and statistics that can be used for regional regression. Methods used to compute the summary statistics contained in this data release are described in an accompanying report (Armstrong and others, 2025).

In 2016, non-interpretive streamflow statistics were compiled for streamgages located throughout the Nation and stored in the StreamStatsDB database for use with StreamStats and other applications. Two previously published USGS computer programs that were designed to help calculate streamflow statistics were updated to better support StreamStats as part of this effort. These programs are named “GNWISQ” (Get National Water Information System Streamflow (Q) files) and “QSTATS” (Streamflow (Q) Statistics). Statistics for 20,438 streamgages that had 1 or more complete years of record during water years 1901 through 2015 were calculated from daily mean streamflow data; 19,415 of these streamgages were within the conterminous United States. About 89 percent of the 20,438 streamgages had 3 or more years of record, and 65 percent had 10 or more years of record. Drainage areas of the 20,438 streamgages ranged from 0.01 to 1,144,500 square miles. The magnitude of annual average streamflow yields (streamflow per square mile) for these streamgages varied by almost six orders of magnitude, from 0.000029 to 34 cubic feet per second per square mile. About 64 percent of these streamgages did not have any zero-flow days during their available period of record. The 18,122 streamgages with 3 or more years of record were included in the StreamStatsDB compilation so they would be available via the StreamStats interface for user-selected streamgages.

This dataset represents 19,031 basin boundaries and their streamgage locations for the U.S. Geological Survey's (USGS) active and historical streamgages from the published dataset of Stewart and others (2006) and its subsequent updates (D.W. Stewart, USGS, written commun., 2011). Only the basin boundaries that were delineated within 15 percent of the basin area reported in the National Water Information System (NWIS) were included in this dataset. This dataset only includes streamgage basins in the lower 48 states and not in Alaska, Hawaii, or Puerto Rico. The basin boundaries and streamgage locations are provided in 18 shapefiles separated by 2-digit Hydrologic Unit Code. The USGS streamgage station's identification number attached to each delineated polygon can be linked to the attribute data found in Stewart and others (2006). The delineated watersheds were made from digital elevation models found in the NHDPlus data suite (version 1, 2006) and based on gage locations provided by Stewart and others (2006). These basins have been used in several USGS studies such as James Falcone's "GAGES-II: Geospatial Attributes of Gages for Evaluating Streamflow" (2011) and Xiaodong Jian and others, "WaterWatch-Maps, Graphs, and Tables of Current, Recent, and Past Streamflow Conditions " (2008).

This dataset represents 19,031 basin boundaries and their streamgage locations for the U.S. Geological Survey's (USGS) active and historical streamgages from the published dataset of Stewart and others (2006) and its subsequent updates (D.W. Stewart, USGS, written commun., 2011). Only the basin boundaries that were delineated within 15 percent of the basin area reported in the National Water Information System (NWIS) were included in this dataset. This dataset only includes streamgage basins in the lower 48 states and not in Alaska, Hawaii, or Puerto Rico. The basin boundaries and streamgage locations are provided in 18 shapefiles separated by 2-digit Hydrologic Unit Code. The USGS streamgage station's identification number attached to each delineated polygon can be linked to the attribute data found in Stewart and others (2006). The delineated watersheds were made from digital elevation models found in the NHDPlus data suite (version 1, 2006) and based on gage locations provided by Stewart and others (2006). These basins have been used in several USGS studies such as James Falcone's "GAGES-II: Geospatial Attributes of Gages for Evaluating Streamflow" (2011) and Xiaodong Jian and others, "WaterWatch-Maps, Graphs, and Tables of Current, Recent, and Past Streamflow Conditions " (2008).