Lake Winnebago

  • 131,1939 acres
  • Max Depth 21 feet
  • Counties: Winnebago, Calumet, Fond du Lac

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 River’s 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 commercial shipping, and now recreational boating.  In winter the water levels are lowered to prevent ice damage, which probably provides little if any protection, and to make room for spring melt water.

Sunrise over Miller’s Bay and Lake Winnebago

The operation of these dams has had major impacts on 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.

Zebra Mussel Beach

The Zebra Mussel (Dreissena polymorpha) has had an effect on Lake Winnebago, especially where there are plenty of rocks for them to attach to, but just how much it is difficult to say. Zebra mussels pull algae and zooplankton from the water column, clearing the water to some extent. They deposit their waste on the lake floor obviously, this changes where nutrients are in the lake. What all this does has actually done to Winnebago is unknown, but it has drastically changed Lake Michigan. The windrows of zebra mussel shells in this photo are located at Wayside Park on the Southwest shore of the lake.

Great Egret Nest

Three baby-blue Great Egret (Ardea alba) eggs, in a nest made in a honeysuckle bush of all places.

Lake Flies

As the sun goes down the lake flies rise from their daytime hiding places, like this spruce tree at Menominee Park in Oshkosh. Newly emerged flies rise from the lake. The Lake Fly is one of the major drivers of Lake Winnebago’s sport fishery, either directly or indirectly.