Hydrological Unit Maps

Author: Federal

Media Type: Website

Water Monitoring Keywords: Mapping Tools

Water Resource Type: Broadly Applicable

Resource Link: https://water.usgs.gov/GIS/huc.html

Specific Agency Author: United States Geological Survey (USGS)

The United States is divided and sub-divided into successively smaller hydrologic units which are classified into four levels: regions, sub-regions, accounting units, and cataloging units. The hydrologic units are arranged or nested within each other, from the largest geographic area (regions) to the smallest geographic area (cataloging units). Each hydrologic unit is identified by a unique hydrologic unit code (HUC) consisting of two to eight digits based on the four levels of classification in the hydrologic unit system.