Wisconsin's Hydrologic Areas

Major Basins
Water Management Units (WMUs)
Geographic Management Units (GMUs)
Watersheds
Hydrologic Unit Codes (HUCs)

1. Major Basins

Purpose: To identify the major drainage patterns of Wisconsin. The state is divided into 3 major river basins each identified by the primary waterbody into which the basin drains. In Wisconsin, they are the Lake Superior Basin, Mississippi River Basin and the Lake Michigan Basin.

Relationship to HUCs (exit DNR): Closely resemble the HUC "Regions" (Level 1, 2-digit Hydrologic Unit Hierarchy HUC)).

Map: Wisconsin Major Basins (Lake Superior, Lake Michigan and Mississippi River)




2. Water Management Units (WMUs)

Purpose: These areas are hydrologically based subdivisions of the larger Major Basins of the state. Wisconsin has 24 Water Management Units that were originally developed to support the old Water Quality Management Plans (a.ka. Basin Plans). Water Quality Management Plans are now being replaced by the State of the Basin Reports. In almost all cases of the State of the Basin Reports, the GMU boundaries are used (see #3 below). Exceptions are the Lower Chippewa, Central Wisconsin).

Relationship to HUCs (exit DNR): Approximately equivalent to "Regions" (Level 4, 8-digit Hydrologic Unit Hierarchy (HUC)).

Map: 24 Water Management Units




3. Geographic Management Units (GMUs)

Purpose: 23 Geographic Management Units were developed largely to help define where work activities of some WDNR staff begin and end.

Relationship to HUC (exit DNR): Somewhat similar to HUC "Basins" 4th level, 8-digit HUC but differ because they incorporate county boundaries and are therefore not entirely hydrologically based.

Map: 23 Geographic Management Units (GMUs)




4. Watersheds

Purpose: Used to manage water resources at the local level. These units have also primarily been used to prepare reference base maps for the NPS Priority Watershed Program. They are a further hydrologic subdivision of the Water Management Units.

Relationship to HUCs (exit DNR): Approximately equivalent to HUC "Watershed" (Level 5, 10-digit Hydrologic Unit Hierarchy (HUC)).

Map: 334 Watersheds


5. Hydrologic Unit Codes (HUCs)

Purpose: In coordination with EPA and state environmental agencies, NRCS and USGS are developing a nationwide digital watershed boundary dataset. The dataset is comprised of nested regions that delineate progressively smaller watersheds, which are called hydrologic units (HUCs). Each hydrologic unit has a code assigned to it, called a hydrologic unit code (HUC). A HUC is a series of two-digit groupings of numbers that describe a hydrologic unit’s scale, plus where it fits in the larger hydrologic unit framework.

More about HUCs can be read in this document "About HUCs", 2008[Word 530KB]

Below is a representation of the 8-digit HUCs that intersect the state of Wisconsin, which includes HUCs that extend down to the mouths of the Rock and Des Plaines Rivers, as well as HUCs for the Montreal and Brule Rivers that straddle the WI-MI line

Contact

For more information contact:

Ann Schachte Or
Matt Rehwald Water Division