Lake Winnebago

  • 131,1939 acres
  • Max Depth 21 feet
  • Counties: Winnebago, Calumet, Fond du Lac
Zebra Mussel Beach
The shells of Zebra Mussels (Dreissena polymorpha), an aquatic invasive species (AIS) pile up on windrows on the beach of Lake Winnebago, causing problems for beach combers. The living Zebra Mussels in the lake change the lake’s environment by filtering out large amounts of algae, preventing other animals from feeding on it.

Lake Winnebago is the largest lake in the state of Wisconsin.  It was carved out by the Green Bay Lobe of the great Wisconsin Glacier.  The nice depression left by the glacier may have not become a lake if it hadn’t been for the natural dam at the outlet of the lake.  This natural dam backs up the Fox River creating the lake.  Beginning in 1849 industry built two  dams at the outlet of Lake Winnebago to tap the Fox Rivers energy to power industry.  The height of these dams was increased over the years and are used to keep the level of Lake Winnebago high in the summer for recreational boating, and low in the winter to prevent ice damage and provide some room for spring runoff.

The operation of these dams has had major impacts on the natural world.  From 1850 to 1960, it created an environmental catastrophe and today contributes to a slow decline in aquatic habitat, particularly on the Upper Pool Lakes.  See the Habitat Loss page for more information.