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.

This data release contains daily time series estimates of natural streamflow at 5,439 GAGES-II non-reference streamgages in 19 study regions across the conterminous United States from October 1, 1980 through September 30, 2017, using five statistical techniques: nearest-neighbor drainage area ratio (NNDAR), map-correlation drainage area ratio (MCDAR), nearest-neighbor nonlinear spatial interpolation using flow duration curves (NNQPPQ), map-correlation nonlinear spatial interpolation using flow duration curves (MCQPPQ), and ordinary kriging of the logarithms of discharge per unit area (OKDAR). NNDAR, MCDAR, NNQPPQ, and MCQPPQ estimates were computed following methods described in Farmer and others (2014), with updates to the flow-duration curve modeling which is described in Over and others (2018). OKDAR estimates were computed using pooled variograms for each study region following methods described in Farmer (2016). Daily streamflow estimation was conducted by study region (hydrologic unit code level-2 regions as defined in Falcone, 2011) by building statistical models using 1,385 GAGES-II reference streamgages from mostly undisturbed watersheds as index gages (Russell and others, 2020). Estimates were then made at GAGES-II non-reference streamgages. Location information and basin characteristics for study gages were obtained from the GAGES-II dataset (Falcone, 2011). Observed daily streamflow data were retrieved from the National Water Information System (USGS, 2019). This data release contains 19 separate zip files; one for each study region. Each zip file contains an individual tab-delimited text file for each non-reference streamgage in the study region. A text file summarizing period of record information for each non-reference streamgage is provided (non-reference_gages_summary.csv). This data release also contains a text file (Model_info.csv) of regional regression equations for 27 flow quantiles that were developed in each study region in order to implement the QPPQ methods and a text file (BC_transformations.csv) describing transformations made to the GAGES-II derived basin characteristics prior to use in the regression equations. The five sets of streamflow estimates represent expected natural streamflow conditions with minimal disturbance by human activities, in other words, without the effects of regulation, diversion, land development, or other anthropogenic activities. The observed streamflow records at the non-reference streamgages were compared to the five simulated streamflow records. These performance metrics are provided at each gage for all five statistical methods (NonRef_PMs_byStation.csv) and as summaries by region (NonRef_PM_summaries_byRegion.csv). References cited: Falcone, J.A., 2011, GAGES-II: Geospatial Attributes of Gages for Evaluating Streamflow [digital spatial dataset]: U.S. Geological Survey Water Resources NSDI Node web page, https://water.usgs.gov/lookup/getspatial?gagesII_Sept2011. Farmer, W.H., Archfield, S.A., Over, T.M., Hay, L.E., LaFontaine, J.H., and Kiang, J.E., 2014, A comparison of methods to predict historical daily streamflow time series in the southeastern United States: U.S. Geological Survey Scientific Investigations Report 2014–5231, 34 p., http://dx.doi.org/10.3133/sir20145231. Farmer, W. H., 2016, Ordinary kriging as a tool to estimate historical daily streamflow records, Hydrology and Earth System Sciences, 20, 2721-2735, https://doi.org/10.5194/hess-20-2721-2016. Over, T.M., Farmer, W.H., and Russell, A.M., 2018, Refinement of a regression-based method for prediction of flow-duration curves of daily streamflow in the conterminous United States: U.S. Geological Survey Scientific Investigations Report 2018–5072, 34 p., https://doi.org/10.3133/sir20185072. Russell, A.M., Over, T.M., and Farmer, W.H., 2020, Cross-validation results for five statistical methods of daily streamflow estimation at 1,385 reference streamgages in the conterminous United States, Water Years

This data release contains daily time series estimates of natural streamflow at 5,439 GAGES-II non-reference streamgages in 19 study regions across the conterminous United States from October 1, 1980 through September 30, 2017, using five statistical techniques: nearest-neighbor drainage area ratio (NNDAR), map-correlation drainage area ratio (MCDAR), nearest-neighbor nonlinear spatial interpolation using flow duration curves (NNQPPQ), map-correlation nonlinear spatial interpolation using flow duration curves (MCQPPQ), and ordinary kriging of the logarithms of discharge per unit area (OKDAR). NNDAR, MCDAR, NNQPPQ, and MCQPPQ estimates were computed following methods described in Farmer and others (2014), with updates to the flow-duration curve modeling which is described in Over and others (2018). OKDAR estimates were computed using pooled variograms for each study region following methods described in Farmer (2016). Daily streamflow estimation was conducted by study region (hydrologic unit code level-2 regions as defined in Falcone, 2011) by building statistical models using 1,385 GAGES-II reference streamgages from mostly undisturbed watersheds as index gages (Russell and others, 2020). Estimates were then made at GAGES-II non-reference streamgages. Location information and basin characteristics for study gages were obtained from the GAGES-II dataset (Falcone, 2011). Observed daily streamflow data were retrieved from the National Water Information System (USGS, 2019). This data release contains 19 separate zip files; one for each study region. Each zip file contains an individual tab-delimited text file for each non-reference streamgage in the study region. A text file summarizing period of record information for each non-reference streamgage is provided (non-reference_gages_summary.csv). This data release also contains a text file (Model_info.csv) of regional regression equations for 27 flow quantiles that were developed in each study region in order to implement the QPPQ methods and a text file (BC_transformations.csv) describing transformations made to the GAGES-II derived basin characteristics prior to use in the regression equations. The five sets of streamflow estimates represent expected natural streamflow conditions with minimal disturbance by human activities, in other words, without the effects of regulation, diversion, land development, or other anthropogenic activities. The observed streamflow records at the non-reference streamgages were compared to the five simulated streamflow records. These performance metrics are provided at each gage for all five statistical methods (NonRef_PMs_byStation.csv) and as summaries by region (NonRef_PM_summaries_byRegion.csv). References cited: Falcone, J.A., 2011, GAGES-II: Geospatial Attributes of Gages for Evaluating Streamflow [digital spatial dataset]: U.S. Geological Survey Water Resources NSDI Node web page, https://water.usgs.gov/lookup/getspatial?gagesII_Sept2011. Farmer, W.H., Archfield, S.A., Over, T.M., Hay, L.E., LaFontaine, J.H., and Kiang, J.E., 2014, A comparison of methods to predict historical daily streamflow time series in the southeastern United States: U.S. Geological Survey Scientific Investigations Report 2014–5231, 34 p., http://dx.doi.org/10.3133/sir20145231. Farmer, W. H., 2016, Ordinary kriging as a tool to estimate historical daily streamflow records, Hydrology and Earth System Sciences, 20, 2721-2735, https://doi.org/10.5194/hess-20-2721-2016. Over, T.M., Farmer, W.H., and Russell, A.M., 2018, Refinement of a regression-based method for prediction of flow-duration curves of daily streamflow in the conterminous United States: U.S. Geological Survey Scientific Investigations Report 2018–5072, 34 p., https://doi.org/10.3133/sir20185072. Russell, A.M., Over, T.M., and Farmer, W.H., 2020, Cross-validation results for five statistical methods of daily streamflow estimation at 1,385 reference streamgages in the conterminous United States, Water Years

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 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 contains 29 streamflow statistics computed from modeled and observed daily streamflows from October 1, 1983, through September 30, 2016 at 1,114 streamgages in 19 study regions covering the conterminous United States. The streamflow statistics were computed at selected GAGES-II reference streamgages (Falcone, 2011) from daily streamflow observations (Russell and others, 2020), from daily streamflow time series computed using the National Hydrologic Model-Precipitation Runoff Modeling System (NHM-PRMS) model (“by headwater” and “by observation” calibrations with Muskingum routing; Hay and LaFontaine, 2020), from daily streamflow time series computed using five statistical time series models (Russell and others, 2020), and from three direct statistical prediction methods (Over and others, unpub. data, 2020). The data release comprises twelve .csv files. The streamflow statistics values are provided in eleven of these files, one each for the observed, the two NHM-PRMS calibrations, the five statistical time series models, and the three direct statistical prediction methods. The remaining file is a summary table, which provides period-of-record information for each streamgage. References cited: Falcone, J.A., 2011, GAGES-II: Geospatial Attributes of Gages for Evaluating Streamflow [digital spatial dataset] : U.S. Geological Survey Water Resources NSDI Node web page, https://water.usgs.gov/lookup/getspatial?gagesII_Sept2011. Hay, L.E., and LaFontaine, J.H., 2020, Application of the National Hydrologic Model Infrastructure with the Precipitation-Runoff Modeling System (NHM-PRMS),1980-2016, Daymet Version 3 calibration: U.S. Geological Survey data release, https://doi.org/10.5066/P9PGZE0S Russell, A.M., Over, T.M., and Farmer, W.H., 2020, Cross-validation results for five statistical methods of daily streamflow estimation at 1,385 reference streamgages in the conterminous United States, Water Years 1981-2017: U.S. Geological Survey data release, https://doi.org/10.5066/P9XT4WSP

This data release contains 29 streamflow statistics computed from modeled and observed daily streamflows from October 1, 1983, through September 30, 2016 at 1,114 streamgages in 19 study regions covering the conterminous United States. The streamflow statistics were computed at selected GAGES-II reference streamgages (Falcone, 2011) from daily streamflow observations (Russell and others, 2020), from daily streamflow time series computed using the National Hydrologic Model-Precipitation Runoff Modeling System (NHM-PRMS) model (“by headwater” and “by observation” calibrations with Muskingum routing; Hay and LaFontaine, 2020), from daily streamflow time series computed using five statistical time series models (Russell and others, 2020), and from three direct statistical prediction methods (Over and others, unpub. data, 2020). The data release comprises twelve .csv files. The streamflow statistics values are provided in eleven of these files, one each for the observed, the two NHM-PRMS calibrations, the five statistical time series models, and the three direct statistical prediction methods. The remaining file is a summary table, which provides period-of-record information for each streamgage. References cited: Falcone, J.A., 2011, GAGES-II: Geospatial Attributes of Gages for Evaluating Streamflow [digital spatial dataset] : U.S. Geological Survey Water Resources NSDI Node web page, https://water.usgs.gov/lookup/getspatial?gagesII_Sept2011. Hay, L.E., and LaFontaine, J.H., 2020, Application of the National Hydrologic Model Infrastructure with the Precipitation-Runoff Modeling System (NHM-PRMS),1980-2016, Daymet Version 3 calibration: U.S. Geological Survey data release, https://doi.org/10.5066/P9PGZE0S Russell, A.M., Over, T.M., and Farmer, W.H., 2020, Cross-validation results for five statistical methods of daily streamflow estimation at 1,385 reference streamgages in the conterminous United States, Water Years 1981-2017: U.S. Geological Survey data release, https://doi.org/10.5066/P9XT4WSP

This dataset contains a zipped file (dailyQs.zip) of daily streamflow data for 1,378 streamgages in 19 study regions in the conterminous U.S. from October 1, 1980 through September 30, 2013 from mostly undisturbed watersheds. USGS streamgages that were identified as being of “reference” quality in the GAGES-II dataset (https://water.usgs.gov/lookup/getspatial?gagesII_Sept2011) and had at least 10 complete water years (WYs) during the study period from WY1981 through WY2013 were selected. Daily streamflow data were retrieved from the National Water Information System (NWIS) on April 18, 2016. This dataset also contains an Excel file (compWYs.xlsx) indicating for each WY during the study period whether a streamgage had a complete streamflow record (no missing values) during that year. Only complete WYs of daily streamflow data during the study period from the selected streamgages were used to compute the empirical FDC quantiles to which regression equations were fitted. These data support a concurrent publication (Over and others, 2018).

This dataset contains annual peak and seasonal maximum streamflow data from the USGS National Water Information System (NWIS) and the results of an analysis of spatial and temporal patterns for those data for the conterminous U.S. An interpretation of the analysis of these data will be published in a journal article. The streamflow data were compiled for the years 1966 to 2015 for 415 streamgages that are part of the USGS HCDN-2009 network. The HCDN-2009 network contains streamgages in watersheds with minimal anthropogenic change. The dataset contains the annual peak and the maximum daily streamflow for the months of October through December (OND), January through March (JFM), April through June (AMJ), and July through September (JAS). The maximum daily streamflow for OND, JFM, AMJ, and JAS was determined as the largest daily streamflow over those months. This dataset contains the following files for the annual peaks and maximum daily streamflow. The files labeled "raw" contain the water year and the raw annual peaks from NWIS and the selected maximum daily streamflow from NWIS. The files labeled "SPI" contain the water year and the standardized peaks and maximum daily streamflow by using the Standardized Precipitation Index method. The files labeled "cluster_assignments" contain (in columns) the gage name (two letter abbreviation of the state in which the gage is located and the USGS site number), the latitude and longitude (NAD 83) of the gage, an integer that is an identifier of the cluster that the gage was assigned, and the Pearson correlation coefficient between the standardized streamflow and the average standardized streamflow of all gages in its cluster. The annual peaks were clustered into 4 groups, the OND maximum flows were clustered into 7 groups, the JFM maximum flows were clustered into 9 groups, and the both the AMJ and JAS maximum flows were clustered into 5 groups. The files with the term "cluster_means" in the file name contain the water year and the mean of the standardized streamflow of all gages in the clusters of peaks and maximum daily streamflow for OND, JFM, AMJ, and JAS.

This dataset contains annual peak and seasonal maximum streamflow data from the USGS National Water Information System (NWIS) and the results of an analysis of spatial and temporal patterns for those data for the conterminous U.S. An interpretation of the analysis of these data will be published in a journal article. The streamflow data were compiled for the years 1966 to 2015 for 415 streamgages that are part of the USGS HCDN-2009 network. The HCDN-2009 network contains streamgages in watersheds with minimal anthropogenic change. The dataset contains the annual peak and the maximum daily streamflow for the months of October through December (OND), January through March (JFM), April through June (AMJ), and July through September (JAS). The maximum daily streamflow for OND, JFM, AMJ, and JAS was determined as the largest daily streamflow over those months. This dataset contains the following files for the annual peaks and maximum daily streamflow. The files labeled "raw" contain the water year and the raw annual peaks from NWIS and the selected maximum daily streamflow from NWIS. The files labeled "SPI" contain the water year and the standardized peaks and maximum daily streamflow by using the Standardized Precipitation Index method. The files labeled "cluster_assignments" contain (in columns) the gage name (two letter abbreviation of the state in which the gage is located and the USGS site number), the latitude and longitude (NAD 83) of the gage, an integer that is an identifier of the cluster that the gage was assigned, and the Pearson correlation coefficient between the standardized streamflow and the average standardized streamflow of all gages in its cluster. The annual peaks were clustered into 4 groups, the OND maximum flows were clustered into 7 groups, the JFM maximum flows were clustered into 9 groups, and the both the AMJ and JAS maximum flows were clustered into 5 groups. The files with the term "cluster_means" in the file name contain the water year and the mean of the standardized streamflow of all gages in the clusters of peaks and maximum daily streamflow for OND, JFM, AMJ, and JAS.