John C Hammond 20250520 tabular digital data https://doi.org/10.5066/P1DESGMW This dataset contains topographic, climatic and land cover attributes for headwaters (stream orders 1 and 2 ) as defined by the National Hydrography Dataset High Resolution (NHDHR) and downstream areas (stream orders 3 and up) for a subset of Conterminous United States (CONUS) HUC12s. Specifically, this dataset contains 2021 National Land Cover Database (NLCD) land cover for the following categories: water, developed, forest, shrubland/grassland, crops/hay; topographic metrics including: area, slope, elevation, stream density, stream length, stream slope and depth to bedrock; climatic metrics including aridity and snow persistence; and soil metrics including clay, silt and sand. This dataset was compiled to support analysis looking at similarities and differences between headwater areas across CONUS, and to assess differences between headwater and downstream areas. 20250415 ground condition Complete None planned -128.3203 -65.9180 49.8380 24.0465 ISO 19115 Topic Category inlandWaters climatologyMeteorologyAtmosphere None catchments headwaters streams USGS Metadata Identifier USGS:67fffc34d4be020983ea0055 None conterminous United States 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. John Hammond U.S. Geological Survey Maryland Delaware D.C. Water Science Center Research Hydrologist mailing and physical

5522 Research Park Drive

Catonsville Maryland 21228 USA 4434985568 jhammond@usgs.gov Land cover, topographic, soils and climate extractions were randomly checked by comparisons to underlying gridded data. 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. This datasets represents a complete HUC12 coverage of the Conterminous United States. Transboundary and coastal areas were removed in cases where there was not complete coverage of all datasets for select HUC12s. Susan G. Buto Rebecca D. Anderson 20250101 publication n/a US Geological Survey https://doi.org/10.3133/fs20203033 Digital and/or Hardcopy 20250101 publication date NHDHR Stream network and headwater catchments John T. Abatzoglou 20111221 publication International Journal of Climatology vol. 33, issue 1 n/a Wiley ppg. 121-131 https://doi.org/10.1002/joc.3413 Digital and/or Hardcopy 20241001 publication date gridMET aridity values Laura Poggio Luis M. de Sousa Niels H. Batjes Gerard B. M. Heuvelink Bas Kempen Eloi Ribeiro David Rossiter 20210614 publication SOIL vol. 7, issue 1 n/a Copernicus GmbH ppg. 217-240 https://doi.org/10.5194/soil-7-217-2021 Digital and/or Hardcopy 20210614 publication date soilgrids Sand, silt and clay values Jon Dewitz 20230101 dataset https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/p9jz7ao3 Digital and/or Hardcopy 20230101 publication date NLCD2021 Land cover values Yan Liu David Tarboton David Maidment 20201231 publication n/a Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Oak Ridge Leadership Computing Facility (OLCF); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States) https://doi.org/10.13139/ornlnccs/1630903 Digital and/or Hardcopy 20201231 publication date HAND Height above nearest drainage values John C Hammond 2020 dataset https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/p9u7u5fp Digital and/or Hardcopy 20201231 publication date Snow persistence Snow persistence values Xiao Huang 2020 publication n/a Harvard Dataverse https://doi.org/10.7910/dvn/dlgp7y Digital and/or Hardcopy 20201001 publication date Population Population estimate OpenTopography 20211231 publication n/a OpenTopography https://doi.org/10.5069/g98k778d Digital and/or Hardcopy 20211231 publication date Elevation Elevation from USGS 3DEP Numerous gridded datasets as listed in the source inputs section ranging from 4km to 30 meter spatial resolution were extracted as catchment average values or sums separately for headwater (stream orders 1 and 2 as defined by NHD high resolution) and downstream areas (stream orders 3 and up as defined by NHD high resolution) for Conterminous United States (CONUS) HUC12s. Specifically, an extraction was performed for each HUC12 once for headwaters, and once for downstream areas. The coefficient of variation was also calculated using all cells intersecting with each polygon. For all zonal statistic aggregations area-weighted calculations were made using the exactextractr (Baston, 2020: doi.10.32614/CRAN.package.exactextractr) R package. Headwater and downstream units were generated from the NHDHR dataset and represent the area drained just by stream orders 1 and 2 (headwaters) or stream orders 3 and up (downstream). Height above nearest drainage (HAND) values were classified into deep (>15 meters), shallow (5-15 meters), and surface (<5 meters) and the total area in each category was summarized for each headwater or downstream unit. R version 4.4.0 Exactextractr version 0.10.0 20241215 headwaters_extracts_04142025_QAQCed.csv Comma Separated Value (CSV) file containing data. Producer Defined huc12 The twelve digit hydrologic unit code for this specific headwater or downstream unit USGS Defined 010100020101 181002041600 unitless hw SO12 for headwaters unit, SO3plus for downstream USGS Defined SO12 stream order 1 or two: headwaters USGS defined SO3plus stream order 3 and up: downstream USGS defined water_percent Percent of HUC12 headwaters or downstream unit in water from NLCD 2021 USGS Defined 0.0 100.0 percent developed_percent Percent of HUC12 headwaters or downstream unit in developed (dev high + dev med + dev low + dev open) from NLCD 2021 USGS Defined 0.0 100.0 percent forest_percent Percent of HUC12 headwaters or downstream unit in forest (mixed forest + evergreen forest + deciduous forest) from NLCD 2021 USGS Defined 0.0 100.0 percent shrubgrass_percent Percent of HUC12 headwaters or downstream unit in shrubland from NLCD 2021 USGS Defined 0.0 100.0 percent crophay_percent Percent of HUC12 headwaters or downstream unit in crop or hay from NLCD 2021 USGS Defined 0.0 100.0 percent area_km2 Area of the headwaters or downstream area in the specific HUC12 USGS Defined 0.0009 7133.5314 square kilometers slope_mean Average slope across the spatial unit. Derived from 10 meter USGS 3DEP DEMS. USGS Defined 0.0 37.2660484313965 degrees slope_cv Coefficient of variation of slope across the spatial unit. Derived from 10 meter USGS 3DEP DEMS. USGS Defined 0.0 106.207229614258 unitless elev_mean Average elevation across the spatial unit. Derived from 10 meter USGS 3DEP DEMS. USGS Defined -72.01422119140621 3753.875 meters elev_cv Coefficient of variation of elevation across the spatial unit. Derived from 10 meter USGS 3DEP DEMS. USGS Defined -66.61590576171879 48.156612396240206 unitless pop_sum Total population across the spatial unit USGS Defined 0.0 1531122.875 people pop_cv Coefficient of variation of population across the spatial unit USGS Defined 0.0 17.2541828155518 unitless sp_mean AVerage snow persistence across the spatial unit, which is the fraction of time snow is on the ground between January and July USGS Defined 0.0 95.8328018188477 percent sp_cv Coefficient of variation of snow persistence across the spatial unit USGS Defined 0.0 3305.49829101562 unitless aridity_mean Average aridity across the spatial unit USGS Defined 0.12360429018735901 33.1370849609375 unitless aridity_cv Coefficient of variation of aridity across the spatial unit USGS Defined 0.0 1.08684003353119 unitless SND_mean Average sand percent across the spatial unit USGS Defined 1.62850368022919 89.2727813720703 percent SND_cv Coefficient of variation of sand percent across the spatial unit USGS Defined 0.0 1.58245277404785 unitless CLY_mean Average clay percent across the spatial unit USGS Defined 2.51232051849365 62.6994094848633 CLY_cv Coefficient of variation of clay percent across the spatial unit USGS Defined 0.0 0.8745911121368409 unitless SLT_mean Average silt percent across the spatial unit USGS Defined 5.700147151947019 71.8625030517578 SLT_cv Coefficient of variation of silt percent across the spatial unit USGS Defined 0.0 0.866105020046234 unitless bedrock_mean Average depth to bedrock across the spatial unit USGS Defined 0.547246813774109 56130.328125 bedrock_cv Coefficient of variation of depth to bedrock across the spatial unit USGS Defined 0.0 15.2495431900024 unitless headwaters SO12 for headwaters unit, SO3plus for downstream USGS Defined SO12 stream orders 1 or 2 USGS defined SO3plus stream orders 3 and up USGS defined surface_percent Percent of the HUC12 headwater or downstream unit that is classified as having a surface water table USGS Defined << empty cell >> No Data Producer defined 0.0 1.0 percent shallow_percent Percent of the HUC12 headwater or downstream unit that is classified as having a shallow water table USGS Defined << empty cell >> No Data Producer defined 0.0 1.0 percent deep_percent Percent of the HUC12 headwater or downstream unit that is classified as having a deep water table USGS Defined << empty cell >> No Data Producer defined 0.0 1.0 percent HUC2 HUC2 that the HUC12 falls within USGS Defined 1 18 HUC4 HUC4 that the HUC12 falls within USGS Defined 0101 1810 DIVISION USGS physiographic division assigned to the HUC12 centroid point USGS Defined << empty cell >> Centroid point not assigned to a USGS physiographic region Producer defined USGS physiographic division assigned to the HUC12 centroid point PROVINCE USGS physiographic province assigned to the HUC12 centroid point USGS Defined << empty cell >> Centroid point not assigned to a USGS physiographic region Producer defined USGS physiographic province assigned to the HUC12 centroid point SECTION USGS physiographic section assigned to the HUC12 centroid point USGS Defined << empty cell >> Centroid point not assigned to a USGS physiographic region Producer defined USGS physiographic section assigned to the HUC12 centroid point Level_1_ecoregion EPA level 1 ecoregion assigned to the HUC12 centroid point USGS Defined << empty cell >> Centroid point not assigned to an EPA level 1 ecoregion USGS defined EPA level 1 ecoregion assigned to the HUC12 centroid point PercentHWC Percent area of the HUC12 drained by stream order 1 or 2 streams USGS Defined 0.0 100 lat_cent Latitude of the HUC12 centroid point USGS Defined 25.1678 48.9658 decimal degrees long_cent Longitude of the HUC12 centroid point USGS Defined -124.67200000000001 -67.0521 decimal degrees huc12_area_km2 Total area of the HUC12 in square kilometers USGS Defined 0.0174569 8242.76 square kilometers stream_slope_mean Mean stream slope in degrees from NHDHR value added attribute tables. USGS Defined << empty cell >> No Data. NHDHR value added attribute table did not have a value for this HUC12. USGS defined 1e-05 0.802801619047619 stream_slope_cv Coefficient of variation in stream slope in degrees from NHDHR value added attribute tables. USGS Defined << empty cell >> No Data. NHDHR value added attribute table did not have a value for this HUC12. USGS defined 0.0 29.6321117981535 stream_length_km Stream length in km from NHDHR value added attribute tables. Sourced from the NHDHR vallua added attribute tables. USGS Defined << empty cell >> No Data. NHDHR value added attribute table did not have a value for this HUC12. USGS defined 0.006667 3351.099269 stream_density Stream length in km divided by headwaters of downstream area in square km. Sourced from the NHDHR vallua added attribute tables. USGS Defined << empty cell >> No Data. NHDHR value added attribute table did not have a value for this HUC12. USGS defined 0.000713551811974228 inf km/km2 huc12_hw Combination of HUC12 identifier and whether unit is headwaters (SO12) or downstream (SO3plus) USGS Defined Combination of HUC12 identifier and whether unit is headwaters (SO12) or downstream (SO3plus) 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 on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. Digital Data https://doi.org/10.5066/xxxxxxxx None 20250520 John Hammond U.S. Geological Survey Maryland Delaware D.C. Water Science Center Research Hydrologist mailing and physical

5522 Research Park Drive

Catonsville Maryland 21228 USA 4434985568 jhammond@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998