About WDNR's Hydrologic Areas:
- 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)
- 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
- 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)
- 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
Last Revised: Saturday August 18 2007
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