Caelan E. Simeone Leah E. Staub Katharine R. Kolb Sydney S. Foks 20241031 tabular digital data Reston, VA U.S. Geological Survey https://doi.org/10.5066/P9P4DHZE This data release presents truth data and benchmark results describing simulation of hydrologic drought events in the conterminous United States. This data release supports a publication (Simeone and others, 2024) which documents drought benchmarking methods and their application to the results of the National Water Model (NWM) version 2.1. Truth data used were observations at U.S. Geological Survey streamgages across the conterminous United States. These data include 4662 U.S. Geological Survey streamgages with a historical period from 1984-2016. The following files are included in this data release: 1) kappa_long_nwm.csv: Benchmark results for the Cohen's kappa evaluation metrics in long table format. 2) spear_bias_dist_long_nwm.csv: Benchmark results for the Spearman's, bias, and distributional evaluation metrics in long table format. 3) ann_eval_long_nwm.csv: Benchmark results for the annual drought evaluation metrics in long table format. 4) streamflow_percentiles_nwm.zip: A zip file containing individual streamflow percentile data files used in this analysis as truth data. 5) input_data_nwm.zip: A zip file with input data for individual streamgages used for our data analysis pipeline as truth data. 6) streamflow_gages_in_study.csv: Metadata information for the 4662 U.S. Geological Survey streamgages contained in the above datasets. These data were created to benchmark hydrologic model performance with regards to streamflow drought on the basis of daily streamflow for the U.S. Geological Survey Hydro-Terrestrial Earth System Testbed (HyTEST) Project within the Integrated Water Program (IWP). This data also supports the publication: Simeone, C., Foks, S., Towler, E., Hodson, T., and Over, T., 2024. Evaluating Hydrologic Model Performance for Characterizing Streamflow Drought in the Conterminous United States. Water. 1984 2016 ground condition Complete None planned -130.0781 -64.3359 50.6251 23.8858 ISO 19115 Topic Category biota geoscientificInformation inlandWaters USGS Thesaurus hydrology streamflow mathematical modeling datasets hydrographic datasets stream discharge surface water (non-marine) USGS Metadata Identifier USGS:6410bbc9d34e22162d3e163e Geographic Names Information System United States Common Geographic Names CONUS USGS Thesaurus Holocene Era None. Please see 'Distribution Info' for details. None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Caelan E. Simeone U.S. Geological Survey, NW-PACIFIC ISLAND REG Hydrologist mailing address

601 SW 2nd Ave, Suite 1950

Portland OR 97204 US 916-995-0784 gs-w-or_sciencebase@usgs.gov USGS National Water Information System (NWIS), USGS Water Mission Area, USGS Oregon Water Science Center, National Center for Atmospheric Research Windows operating system using R version 4.2 was used to produce this data set. Foks, S.S. Towler, E. Hodson, T.O. Bock, A.R. Dickinson, J.E. Dugger, A.L. Dunne, K.A. Essaid, H.I. Miles, K.A. Over, T.M. Penn, C.A. Russell, A.M. Saxe, S.W. Simeone, C.E. 20220407 publication Reston, VA U.S. Geological Survey https://doi.org/10.5066/P972P42Z National Oceanic and Atmospheric Administration, Office of Water Prediction 2016 publication Tuscaloosa, AL National Oceanic and Atmospheric Administration https://registry.opendata.aws/nwm-archive/ Caelan E. Simeone Sydney Foks Erin Towler Timothy Hodson Thomas Over 2024 publication Accepted in Water Only approved USGS streamflow values were used in the compilation of this dataset. No additional formal accuracy reviews have been conducted. All values of calculated and aggregated streamflow and climate metrics used in this dataset fall within expected ranges and the entries have been checked for duplication and omission. Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the entire metadata record and any attached documentation carefully for additional details. The gages used in this study represent the full sample of USGS watersheds listed in Foks and others (2022) with complete long-term streamflow (as per our auditing conditions) for the respective regions and time periods. Horizontal positions accuracy matches that from the gages input dataset of Foks and others (2022). No vertical positions are provided U.S. Geological Survey 20221231 tabular digital data https://doi.org/10.5066/f7p55kjn Digital and/or Hardcopy 20221231 publication date NWIS Source data provided stream flow information Foks, S.S. Towler, E. Hodson, T.O. Bock, A.R. Dickinson, J.E. Dugger, A.L. Dunne, K.A. Essaid, H.I. Miles, K.A. Over, T.M. Penn, C.A. Russell, A.M. Saxe, S.W. Simeone, C.E. 20220407 tabular digital data https://doi.org/10.5066/P972P42Z Digital and/or Hardcopy 20220401 publication date Cobalt Gages This dataset was was created to be the initial list (version 1.0) for benchmarking streamflow simulated by hydrologic models, and intended for use within the U.S. Geological Survey Hydro-Terrestrial Earth System Testbed (HyTEST) Project within the Integrated Water Program (IWP) Water Resources Mission Area (WMA). The cobalt gages from this dataset were used in conjunction with the streamflow_gages_in_study.csv file in this data release for this study. National Oceanic and Atmospheric Administration, Office of Water Prediction 2016 publication Tuscaloosa, AL National Oceanic and Atmospheric Administration https://registry.opendata.aws/nwm-archive/ Digital and/or Hardcopy 2016 Publication date NWM base input data Falcone, James A. 2011 vector digital data Reston, VA US Geological Survey https://www.sciencebase.gov/catalog/item/631405bbd34e36012efa304a Digital and/or Hardcopy 2011 publication date GAGES-II Reference vs non reference gage categorization David M. Wolock 2003 raster digital data Open File Report 2003-263 Reston, VA US Geological Survey https://www.sciencebase.gov/catalog/item/631405c5d34e36012efa3192 Digital and/or Hardcopy 2003 publication date BFI Base flow index values for the streamgages in the study John C. Hammond Caelan Simeone Jory S. Hecht Glenn A. Hodgkins Melissa Lombard Greg McCabe Dave Wolock Michael Wieczorek Carolyn Olson Todd Caldwell Rob Dudley Adam N. Price 20220830 publication Water Resources Research vol. 58, issue 9 n/a American Geophysical Union (AGU) https://doi.org/10.1029/2022WR031930 Digital and/or Hardcopy 2022 publication date Aridity Methodology for aridity index calculation David M Wolock Gregory J McCabe Michael E Wieczorek 2022 dataset https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/p9etg2rp Digital and/or Hardcopy 2022 publication date Regions Source of regional identifiers. Caelan E. Simeone Sydney S. Foks 2024 publication https://doi.org/10.5066/P1TLARC5 https://code.usgs.gov/wma/hytest/hymed Digital and/or Hardcopy 2024 publication date HyMED This software release contains the workflow used to generate outputs contained in this data release. To generate the evaluation metrics, the National Water Model (NWM) drought simulation data were compared against recorded U.S. Geological Survey streamflow data during periods of drought. The HyMED package was used in R version 4.2.3 to calculate the following evaluation metrics: - Cohen's kappa - Spearman's correlation coefficient - Ratio of standard deviations - Percent bias - Normalized mean absolute error (NMAE) for drought duration, intensity, and severity - Nash Sutcliffe Efficiency (NSE) - Kendall rank correlation coefficient - Mean squared error (MSE) - Pearson correlation coefficient - R squared coefficient of determination - Root mean squared error These calculations are documented in the U.S. Geological Survey software release (Simeone and Foks, 2024) via the HyTEST team. The methodology for this project is described fully in the publication "Evaluating Hydrologic Model Performance for Characterizing Streamflow Drought in the Conterminous United States” (Simeone and others, 2024). 20230322 kappa_long_nwm.csv Comma Separated Value (CSV) file containing data for Cohen's kappa model evaluation metrics for the National Water Model data. U.S. Geological Survey site Eight to 15 digit USGS streamgage identifiers. This field contains leading zeros where they are present in the streamgage ID- consider loading this column as character to retain format. U.S. Geological Survey USGS NWIS station number NWIS threshold The percentile threshold for determining drought, determined based on the percentile of recorded streamflow during the study period for a given gaging station. U.S. Geological Survey 5 30 percentiles pct_type The percentile threshold type, can be either fixed or variable U.S. Geological Survey variable A variable percentile threshold was used. U.S. Geological Survey fixed A fixed percentile threshold was used. U.S. Geological Survey metric The name of the evaluation metric being used U.S. Geological Survey kappa Cohen's kappa, unitless Producer defined classification_accuracy The classification accuracy, unitless U.S. Geological Survey source The model that the metric is evaluating Producer Defined nwm National Water Model v2.1 Producer defined value The resulting value of the evaluation metric U.S. Geological Survey -0.369203432 0.993497604 Units of measure vary and are described in the metric column spear_bias_dist_long_nwm.csv Comma Separated Value (CSV) file containing data for Spearman's, bias, and distributional evaluation metrics for the National Water Model data. There may be multiple entries in this table for one monitoring location, each with varying combinations of threshold, source, and evaluation metric values. U.S. Geological Survey site Eight to 15 digit USGS streamgage identifiers. This field contains leading zeros where they are present in the streamgage ID- consider loading this column as character to retain format. U.S. Geological Survey 8-digit USGS streamgage identifiers NWIS threshold The percentile threshold for determining drought, determined based on the percentile of recorded streamflow during the study period for a given gaging station. U.S. Geological Survey 5 30 percentiles source The model that the metric is evaluating U.S. Geological Survey nwm National Water Model v2.1 U.S. Geological Survey metric The name of the evaluation metric being used U.S. Geological Survey bias Bias between modeled and observed streamflow during periods of observed drought. Units are cubic meter per second (cms). U.S. Geological Survey nse Nash Sutcliffe Efficiency between observed and modeled streamflow during periods of observed drought. Unitless U.S. Geological Survey pct_bias Percent Bias between modeled and observed streamflow during periods of observed drought. Units are percent U.S. Geological Survey rho_obs Spearman's Correlation Coefficient between observed and modeled streamflow during periods of observed drought. Unitless U.S. Geological Survey sd_ratio The ratio of standard deviations between modeled and observed streamflow during periods of observed drought. Unitless U.S. Geological Survey value The resulting value of the evaluation metric U.S. Geological Survey NA No Data or Not Applicable U.S. Geological Survey -417367497591 inf Units of measure vary and are described in the metric column ann_eval_long_nwm.csv Comma Separated Value (CSV) file containing data for annual drought attribute evaluation metrics for the National Water Model data. U.S. Geological Survey site Eight to 15 digit USGS streamgage identifiers. This field contains leading zeros where they are present in the streamgage ID- consider loading this column as character to retain format. Producer Defined USGS NWIS station number NWIS measure The measure of annual drought characteristics. Producer Defined number_of_drought_events The number of distinct drought events Producer defined total_duration_below_threshold The total duration in days below the drought threshold Producer defined total_flow_volume_below_threshold_cms The total flow volume below the threshold in cms days Producer defined total_severity_below_threshold The total drought severity below the threshold in percentile days Producer defined maximum_drought_intensity The percentile distance below the drought threshold of the minimum drought percentile. Producer defined threshold The percentile threshold for determining drought, determined based on the percentile of recorded streamflow during the study period for a given gaging station. Producer Defined 5 30 percentiles type The percentile threshold type, can be either fixed or variable Producer Defined variable A variable percentile threshold was used Producer defined fixed A fixed percentile threshold was used Producer defined mean_obs The mean observed value for this measure Producer Defined NA No Data or Not Applicable U.S. Geological Survey -909.3282758 14171.8561 Units of measure vary and are described in the metric column metric The name of the evaluation metric being used Producer Defined kendall Kendall rank correlation coefficient, unitless Producer defined mae Mean absolute error, in the same units as the measure Producer defined mse Mean squared error, in the same units as the measure Producer defined mspe Mean standard percent error, units of percent Producer defined nmae Normalized mean absolute error, unitless Producer defined NSE Nash Sutcliffe Efficiency, unitless Producer defined pearson Pearson correlation coefficient, unitless Producer defined r2 R squared coefficient of determination, unitless Producer defined rmse Root mean squared error, in the same units as the measure Producer defined spearman Spearman's rank correlation coefficient, unitless Producer defined source The model that the metric is evaluating. Producer Defined nwm National Water Model v2.1 Producer defined value The resulting value of the evaluation metric Producer Defined NA No Data/ Not Applicable Producer defined -30122532761598.6 Inf Units of measure vary and are described in the metric column. input_data_nwm.zip A zipped folder of 4,662 individual Comma Separated Value (CSV) files containing observed and modeled streamflow data. Each file is named in the format XXXXXXXX.csv, where XXXXXXXX is the 8-15 digit code used to identify the streamgage and csv represents the file type U.S. Geological Survey site Eight to 15 digit USGS streamgage identifiers. This field contains leading zeros where they are present in the streamgage ID- consider loading this column as character to retain format. U.S. Geological Survey USGS NWIS station number NWIS dt Date of streamflow measurement U.S. Geological Survey 1984-04-01 2016-03-31 date 1 q_cms_obs Mean daily discharge of observed streamflow in cubic meters per second from NWIS used as truth data U.S. Geological Survey NA No Data/ Not Applicable Producer defined -237.8615113728 11496.63972 cubic meters per second q_cms_nwm Mean daily discharge of National Water Model v2.1 streamflow in cubic meters per second U.S. Geological Survey 0 10564.85 cubic meters per second jd Julian date (or day of calendar year) of the measurement Producer Defined 1 366 days year The calendar year of the measurement. Producer Defined 1984 2016 years month The numerical month of the measurement, for example, January = 1 Producer Defined 1 12 months wy Water year of the measurement (October 1 - September 30) Producer Defined 1984 2016 years cy Climate year of the measurement (April 1 - March 31) Producer Defined 1985 2016 years streamflow_percentiles_nwm.zip A zipped folder of 4,662 individual Comma Separated Value (CSV) files containing observed and modeled streamflow percentiles data. Each file is named in the format XXXXXXXX.csv, where XXXXXXXX is the 8-15 digit code used to identify the streamgage and csv represents the file type. Producer Defined site Eight to 15 digit USGS streamgage identifiers. This field contains leading zeros where they are present in the streamgage ID- consider loading this column as character to retain format. Producer Defined USGS NWIS station number NWIS dt Date of streamflow measurement Producer Defined 1984-04-01 2016-03-31 date q_cms_obs Mean daily discharge of observed streamflow in cubic meters per second from NWIS used as truth data Producer Defined -237.8615114 11496.63972 cubic meters per second q_cms_nwm Mean daily discharge of National Water Model v2.1 streamflow in cubic meters per second Producer Defined 0 10564.85 cubic meters per second jd Julian date (or day of calendar year) of the measurement Producer Defined 1 366 days year The calendar year of the measurement Producer Defined 1984 2016 years month The numerical month of the measurement, for example, January = 1 Producer Defined 1 12 month wy Water year of the measurement (October 1 - September 31) Producer Defined 1984 2016 years cy Climate year of the measurement (April 1 - March 31) Producer Defined 1985 2016 years weibull_jd_obs The observed streamflow percentile using the variable threshold method. Producer Defined 3.0303030303030303 96.96969696969695 percent weibull_jd_nwm The National Water Model streamflow percentile using the variable threshold method Producer Defined 3.03030303 96.96969697 percent weibull_site_obs The observed streamflow percentile using the fixed threshold method Producer Defined 0.008555052 99.99144495 percent weibull_site_nwm The National Water Model streamflow percentile using the fixed threshold method Producer Defined 0.008555052 99.99144495 percent streamflow_gages_in_study.csv Comma Separated Value (CSV) file containing site information metadata for the 4,662 gages used in the HyTEST project U.S. Geological Survey site Eight to 15 digit USGS streamgage identifiers. This field contains leading zeros where they are present in the streamgage ID- consider loading this column as character to retain format. Producer Defined USGS NWIS station number NWIS lat The latitude in decimal degrees of the streamgage. Information was taken from NWIS and is either in North American Datum 1983 or North American Datum 1927 Producer Defined 26.33583333 48.96352778 Decimal Degrees long The longitude in decimal degrees of the streamgage. Information was taken from NWIS and is either in North American Datum 1983 or North American Datum 1927 Producer Defined -124.3929872 -67.725 Decimal Degrees drain_sqkm The drainage area upstream of the streamgage in square kilometers from the cobalt gages dataset (Foks and others, 2022) Producer Defined NA No Data Producer defined 1.1 49802.3 Square kilometers 0.1 aridity The aridity index calculated for each basin as the average monthly precipitation divided by the average monthly potential evapotranspiration Hammond and others (2022) NA Not available Producer defined 0.15 8.02 Unitless 0.01 bfi The base flow index value at the stream gage location. Wolock (2003) 2 87.6 Dimensionless 0.1 class Whether a stream gage is a reference gage or not Falcone (2011) Ref Gage is a reference gage, which showed indicators that they were the least-disturbed watersheds within the GAGES-II dataset Producer defined Non-ref Gage is not a GAGES-II reference gage Producer defined region The regional cluster from Hammond and others 2022 that this streamgage falls in. Gages not in the set used by Hammond and others 2022 were added to the region of the nearest included gage Producer Defined 1-Northeast Northeast region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 2-Northern Mid-Atlantic Northern Mid-Atlantic region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 3-Southern Mid-Atlantic Southern Mid-Atlantic region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 4-Southeast Southeast region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 5-Central plains and forests Central plains and forests region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 6-Northern central Northern central region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 7-Central plains Central plains region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 8-Rocky Mountains Rocky Mountains region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 9-Southwest Southwest region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 10-South central South central region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 11-California and interior west California and interior west region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined 12-Northwest Northwest region as defined by Hammond and others 2022 & McGabe and others 2022 Producer defined GS ScienceBase U.S. Geological Survey mailing address

Denver Federal Center, Building 810, Mail Stop 302

Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. Digital Data https://doi.org/10.5066/P9P4DHZE None 20241031 Caelan E Simeone U.S. Geological Survey, NW-PACIFIC ISLAND REG Hydrologist mailing address

601 SW Second Ave, Suite 1950

Portland OR 97204 US 916-995-0784 gs-w-or_sciencebase@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998