Hydrology Report

A hydrologic unit code is a sequence of numbers or letters that identify a hydrological feature like a river, stream, snow covered area, or a watershed (also called a drainage basin). The USGS maintains a hierarchical system of hydrologic units broken up into regions, sub-regions, accounting units, and cataloging units. Each hydrological area has its own Hydrologic Unit Code (HUC). View hydrology reports by HUC code to get a closer look at river and snow conditions across the US.

Name Level Digits Average Size (Square Miles) Number of Areas Example Name Example HUC Code
Region 1 2 177,560 21 Pacific Northwest 17
Subregion 2 4 16,800 222 Lower Snake 1706
Basin 3 6 10,596 370 Lower Snake 170601
Watershed 4 8 700 2,200 Imnaha River 17060102


Regional Streamflow and Snowpack Comparison


Hydrologic Region Map