WBDHU6: This geospatial dataset represents the 3rd level (6-digit) hydrologic unit boundaries of the Watershed Boundary Dataset (WBD) layer for Washington. It was created by dissolving boundaries from the finer resolution hydrologic units to create these broader boundaries. See metadata for the wbd_wa_poly feature class for a more complete description of the WBD. USGS Federal Standards and Procedures for the National Watershed Boundary Dataset (WBD) located here: http://pubs.usgs.gov/tm/11/a3/pdf/tm11-a3.pdf