Hydrologic Unit Code

The Hydrologic Unit Code (HUC) is a hierarchical land area classification system created by the United States Geological Survey (USGS). It is based on the surface hydrologic features in a standard geographic framework. It is a multi-tiered system, where each level adds two digits to the code in a broad to narrow approach of defining watersheds.

Iowa has two HUC regions - 07 Mississippi River and 10 Missouri River. Within the state, the two most commonly used HUC tiers are the HUC8 (Subbasin) and HUC12 (Subwatershed).

More information on Hydrologic Unit Codes

USGS Hydrologic Unit