Watershed Boundary Dataset (WBD) Facts
- 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.
||Number of HUCs
- 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 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
- Forest Service
- Bureau of Land Management
- Corp of Engineers
- Environmental Protection Agency
- Federal Emergency Management Agency
- National Oceanic and Atmospheric Administration
- National Weather Service