This dataset contains gage information for 75 Hydroclimatic Data Network-2009 basins in the conterminous United States and associated annual runoff volume, winter-spring runoff volume, and winter-spring runoff timing data 1920-2014, as well as trend results for WSCVD and WSV for periods 1920-2014, 1940-2014, and 1960-2014.

This data release identifies 555 Hydro-Climatic Data Network (HCDN) streamgages in the conterminous United States during the period 1981-2019 which were grouped according to similarity in their temporal patterns of mean monthly streamflow.

Peak-flow frequency analysis is crucial in various water-resources management applications, including floodplain management and critical structure design. Federal guidelines for peak-flow frequency analyses, provided in Bulletin 17C, assume that the statistical properties of the hydrologic processes driving variability in peak flows do not change over time and so the frequency distribution of annual peak flows is stationary. Better understanding of long-term climatic persistence and further consideration of potential climate and land-use changes have caused the assumption of stationarity to be reexamined. This data release contains input data and results of a study investigating hydroclimatic trends in peak streamflow (peak flow) in the Central United States, including nine states (Iowa, Illinois, Michigan, Minnesota, Missouri, Montana, North Dakota, South Dakota, and Wisconsin). Peak flow records from unregulated U.S. Geological Survey (USGS) streamgages were used to evaluate changes over 30-, 50-, 75-, and 100-year trend periods, all ending in water year 2020. This data release contains station lists of the streamgages used in each of the nine states, the peak streamflow input data and peak streamflow analysis results, and the climate input data and climate analysis results. See "Station_Lists.zip" on the landing page for station lists (in text file format) for each state included in the study.

Peak-flow frequency analysis is crucial in various water-resources management applications, including floodplain management and critical structure design. Federal guidelines for peak-flow frequency analyses, provided in Bulletin 17C, assume that the statistical properties of the hydrologic processes driving variability in peak flows do not change over time and so the frequency distribution of annual peak flows is stationary. Better understanding of long-term climatic persistence and further consideration of potential climate and land-use changes have caused the assumption of stationarity to be reexamined. This data release contains input data and results of a study investigating hydroclimatic trends in peak streamflow (peak flow) in the Central United States, including nine states (Iowa, Illinois, Michigan, Minnesota, Missouri, Montana, North Dakota, South Dakota, and Wisconsin). Peak flow records from unregulated U.S. Geological Survey (USGS) streamgages were used to evaluate changes over 30-, 50-, 75-, and 100-year trend periods, all ending in water year 2020. This data release contains station lists of the streamgages used in each of the nine states, the peak streamflow input data and peak streamflow analysis results, and the climate input data and climate analysis results. See "Station_Lists.zip" on the landing page for station lists (in text file format) for each state included in the study.

This metadata record describes data that characterize low-flow period duration and seasonality, as well as trends and climate linkages at streamgages across the conterminous United States. These data are associated with a publication which looks to answer three questions about low-flow periods in the conterminous United States: (1) how long are these periods and when do they typically start and end, (2) how are these properties changing through time, and (3) how does climate influence these properties? These data include 1145 U.S. Geological Survey streamgages with historical periods from 1951-2020. This data release contains the following: ===== 1) low_flow_characteristics.csv: Annual low-flow period characteristics for selected streamgages, for each climate year from 1951-2020. 2) low_flow_trends.csv: Trends in low-flow period characteristics for selected streamgages, from 1951-2020. 3) climate_trends.csv: Trends in climate variables for selected streamgages related to low-flow periods from 1951-2020. 4) monthly_low_flows.csv: The number of low-flow days in each month for selected streamgages. 5) site_metadata.csv: Metadata for describing each of the selected streamgages. 6) climate_correlations.csv: Correlations between low-flow period characteristics for selected streamgages and climate variables. 7) all_percentiles_1951_2020.zip: A zip file containing all streamflow percentile data used in this analysis.

This metadata record describes data that characterize low-flow period duration and seasonality, as well as trends and climate linkages at streamgages across the conterminous United States. These data are associated with a publication which looks to answer three questions about low-flow periods in the conterminous United States: (1) how long are these periods and when do they typically start and end, (2) how are these properties changing through time, and (3) how does climate influence these properties? These data include 1145 U.S. Geological Survey streamgages with historical periods from 1951-2020. This data release contains the following: ===== 1) low_flow_characteristics.csv: Annual low-flow period characteristics for selected streamgages, for each climate year from 1951-2020. 2) low_flow_trends.csv: Trends in low-flow period characteristics for selected streamgages, from 1951-2020. 3) climate_trends.csv: Trends in climate variables for selected streamgages related to low-flow periods from 1951-2020. 4) monthly_low_flows.csv: The number of low-flow days in each month for selected streamgages. 5) site_metadata.csv: Metadata for describing each of the selected streamgages. 6) climate_correlations.csv: Correlations between low-flow period characteristics for selected streamgages and climate variables. 7) all_percentiles_1951_2020.zip: A zip file containing all streamflow percentile data used in this analysis.

The datasets herein are the observed instantaneous values of streamflow for the titled U.S. Geological Survey streamgage with precipitation metadata added. Days where streamflow is directly affected by precipitation and the day afterwards is identified with a "B". Two days after a precipitation event is identified with a "C". If the streamflow was affected by snow or ice, the data is identified with a "D". Any data that is not precipitation influenced is identified with an "A". This metadata was applied on the basis of numerous rain gages in the vicinity of the streamgage and radar images obtained from the National Oceanic and Atmospheric Administration website https://www.ncdc.noaa.gov/data-access/radar-data/radar-map-tool (accessed various times throughout the project).

The datasets herein are the observed instantaneous values of streamflow for the titled U.S. Geological Survey streamgage with precipitation metadata added. Days where streamflow is directly affected by precipitation and the day afterwards is identified with a "B". Two days after a precipitation event is identified with a "C". If the streamflow was affected by snow or ice, the data is identified with a "D". Any data that is not precipitation influenced is identified with an "A". This metadata was applied on the basis of numerous rain gages in the vicinity of the streamgage and radar images obtained from the National Oceanic and Atmospheric Administration website https://www.ncdc.noaa.gov/data-access/radar-data/radar-map-tool (accessed various times throughout the project).

Time series of monthly minimum and maximum temperature, precipitation, and potential evapotranspiration were derived for 1,469 watersheds in the conterminous United States for which stream flow measurements were also available from the national streamflow database, termed the Hydro-Climatic Data Network (HCDN), developed by Slack et al. (1993a,b). Monthly climate estimates were derived for the years 1951-1990.The climate characteristic estimates of temperature and precipitation were estimated using the PRISM (Daly et al. 1994, 1997) climate analysis system as described in Vogel, et al. 1999.Estimates of monthly potential evaporation were obtained using a method introduced by Hargreaves and Samani (1982) which is based on monthly time series of average minimum and maximum temperature data along with extraterrestrial solar radiation. Extraterrestrial solar radiation was estimated for each basin by computing the solar radiation over 0.1 degree grids using the method introduced by Duffie and Beckman (1980) and then summing those estimates for each river basin. This process is described in Sankarasubramanian, et al. (2001). Revision Notes: This data set has been revised to update the number of watersheds included in the data set and to updated the units for the potential evapotranspiration variable. Please see the Data Set Revisions section of this document for detailed information.

The supplemental data presented here contain tabular data (in .csv format) including measured and estimated daily and water-year (1982–2016) streamflow for selected watersheds and estimated springflow at Page Springs in Harney Basin. Daily streamflow data are a composite of measured streamflow and extended streamflow records from short-term streamgages in gaged watersheds. Short-term or discontinuous records in gaged watersheds were extended to the period 1982–2016 using the Kendal-Thiel Robust Line (KTRL) method (Helsel and Hirsch, 2020) and ordinary-least squares (OLS) linear regression. Springflow estimates were provided by the U.S. Fish and Wildlife Service.