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Watershed Boundary Dataset (WBD) Facts

History

  • 1974 - USGS / Water Resources Council mapped and published the 2-, 4-, 6-, and 8-digit drainages.
  • 1970's-80's - SCS (now the NRCS) mapped Watersheds and Subwatersheds. (Standards were few and dependent on local use or sponsor needs.)
  • 1992 - SCS National Instruction (NI 170-304) released for Hydrologic Unit mapping and digitizing. Provided a comprehensive set of instructions on delineating boundaries and digitizing.
  • 1996 - Comments received from USGS, FS and BLM on working draft. Many comments incorporated into standard, two delineation criteria differences exist.
  • 2000 - Federal Standards for Delineation of Hydrologic Unit Boundaries out for FGDC-Spatial Water Data Subcommittee member review and comment. Even though it is in draft format, states should be using it as the official guideline in 10 and 12-digit hydrologic unit delineation.
  • 2001 - December 6; The Spatial Water Data Subcommittee approved Version 1.0 of the Federal Standards for Delineation of Hydrologic Unit Boundaries.
  • 2004 - October 1; The Spatial Water Data Subcommittee approved Version 2.0 of the Federal Standards for Delineation of Hydrologic Unit Boundaries.
Watershed Definitions
Name Level Digit Number of HUCs
Region 1 2 21
Subregion 2 4 222
Basin 3 6 352
Subbasin 4 8 2,149
Watershed 5 10 22,000
Subwatershed 6 12 160,000

Criteria

  • Scale at 1:24,000 and the base data meets or exceeds the USGS 7.5 Quad Sheets.
  • Delineation Basis
    • Hydrologically based
    • Crosses stream at confluence
    • May cross at other points if other HUs at same level are upstream
    • No delineations running down stream centerline

Interagency Standard

  • Interagency Standard for Delineation of Hydrologic Unit Boundaries
  • Sponsored by the Federal Geographic Data Committee (FGDC)
  • Subcommittee on Spatial Water Data with members from the:
    • Natural Resources Conservation Service
    • USGS
    • Forest Service
    • Bureau of Land Management
    • Corp of Engineers
    • Environmental Protection Agency
    • Federal Emergency Management Agency
    • National Oceanic and Atmospheric Administration
    • National Weather Service