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Green Lake Facts

Green Lake Facts

Green Lake is Wisconsin’s deepest natural inland lake located in beautiful Green Lake County, Wisconsin. It originated in a valley formed by a pre-glacial river. Glaciation deposited terminal moraines across the western end of the valley (along present-day Highway 73) which impounded the water and created the lake 12,000-23,000 years ago.

GLA Explore Green Lake Map


Big Green Lake Watershed

A watershed is an area of land that water flows across as it moves toward a common body of water, such as a stream, river, lake or coast. Green Lake is part of the Big Green Lake Watershed, which is primarily located in Green Lake County and the remaining 40% extending into Fond du Lac County. A portion of the watershed also edges along the southwest corner of Winnebago County. Green Lake’s outlet is the Puchyan River, which drains into the Fox River and ultimately into Lake Michigan at Green Bay. The Big Green Lake Watershed also includes Spring Lake, Little Twin Lake and Big Twin Lake.

Big Green Lake’s Tributaries

Eight streams, also known as tributaries, flow into Big Green Lake. Some of these tributaries are classified as exceptional waters while others are listed on the impaired waters list. They include: Dakin Creek, Hill Creek, Roy Creek, Wuerches Creek, White Creek, Silver Creek, Spring Creek, Assembly Creek


Charlie Marks, Green Lake Sanitary District Administrator, portages his canoe on Silver Creek.

Green Lake’s Impaired Waters

Fox River Basin

The Upper Fox River Basin

We all live within a river basin. Even if we don’t live near a lake or river, the water on our land still drains to a river, estuary, or lake. Similar to watersheds, water collected in all of the watersheds in a basin flows to a central body of water and out to sea. All of the water in our watershed flows to the Upper Fox River Basin.

Running from the borders of Green Lake and Columbia Counties southwest to Portage and back northeast to Lake Winnebago, the Upper Fox River Basin includes all of Marquette County and portions of Green Lake, Columbia, Fond du Lac, Waushara, Calumet, Adams, and Winnebago Counties.

The Big Green Lake watershed is one of 15 watersheds draining into the Upper Fox River Basin. Three basins, the Upper Fox, Lower Fox, and Wolf Basins flow to Lake Michigan through the Bay of Green Bay. Learn more about the Upper Fox River Basin.

Fast Facts About Green Lake

Deepest natural inland lake in Wisconsin.

  • Greatest Depth 237 ft.
  • Average Depth 100 ft.
  • Surface Area 7,660 acres
  • Length 7.3 miles
  • Width 2 miles
  • Shoreline 27.3 miles

Sources of Water

  • Rainfall 51%
  • Runoff 41%
  • Springs 8%