This dataset at 1:24,000 scale is a greatly expanded version of the hydrologic units created in the mid-1970's by the U.S. Geological Survey under the sponsorship of the Water Resources Council. The WBD is a complete set of hydrologic units from new watershed and subwatesheds less than 10,000 acres to entire river systems draining large hydrologic unit regions, all attributed by a standard nomenclature.
