Watershed Boundary Dataset, 12-Digit Hydrologic Units
The 12-Digit Hydrologic Units, a component of the Watershed Boundary Dataset (WBD), depict the sixth level hydrologic subdivision of the United States. A hydrologic unit can accept surface water from upstream drainage areas and may define a drainage area with single or multiple outlet points. A 12-digit hydrologic unit, or subwatershed, supports water resource management…