Hydrologic Unit

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 … Continued

The 2-Digit Hydrologic Units, a component of the Watershed Boundary Dataset (WBD), depict the major water resource regions of the United States. A water resource region is the first level of classification used by the United States Geological Survey to … Continued