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Lake Kegonsa

Lake Kegonsa

Lake Kegonsa is the lowest lake in the Yahara chain of lakes and is surrounded primarily by agricultural land. Like Waubesa, Lake Kegonsa is one of the shallower lakes in the Yahara chain. Lake Kegonsa State Park, which contains prairie, forest and marsh habitats, is located along its northeastern shore. Most of the phosphorus entering the lake on an annual basis comes from upstream sources. However, summer phosphorus levels may be driven by runoff within the watershed (McDonald & Lathrop, 2016).

The Yahara CLEAN Plan calls for improvements to agricultural cropping practices in this watershed. Reductions to the phosphorus load entering the lake will come from work in the watersheds of the upper lakes. Reductions will also come from improvements to agricultural cropping practices in the Lake Kegonsa Watershed, and decreasing construction erosion in urban areas. Efforts to reduce sources of upstream runoff will reduce the amount of phosphorus entering the lake via the Yahara River outlet (76% of the average annual phosphorus load to the lake).

Lake Kegonsa by the numbers

Yahara Watershed Map
Yahara River Watershed
  • Watershed area: 34,560 acres
  • Surface area: 3,210 acres
  • Shoreline: 10 miles
  • Maximum depth: 31 feet
  • Mean depth: 17 feet
  • Flushing rate: 4 months
Lake Kegonsa Fall Colors
Lake Kegonsa fall colors

How was the water (2019)?

The beach at Lake Kegonsa State Park was closed 11 times in 2019, nine times for cyanobacteria and two times for high E. coli bacteria levels. 2019 average (July – August) water clarity ranked “good” and phosphorus concentrations ranked “poor,” according to Wisconsin DNR criteria for shallow lakes.

2019 community projects & initiatives

  • City of Stoughton converted a bioswale to a wet detention basin in Industrial Park South to better protect water quality. The City collected leaves three times in April and at least seven times in October and November.
  • Friends of Lake Kegonsa Society (FOLKS) continued efforts to harvest carp by offering incentives to commercial anglers. Carp stir up bottom sediments, which resuspends phosphorus and contributes to poor water quality. In 2019, commercial harvesters removed 162,135 pounds of carp. FOLKS also continued to pilot leaf vacuuming with the Town of Dunn, Town of Pleasant Springs, and City of Stoughton, and maintained a native shoreline garden at Fish Camp County Park.

For an update on phosphorus reduction projects, see the State of the Lakes Annual Report.

Organizations supporting the lake

The following groups work on water quality issues in the Lake Kegonsa watershed. Consider contacting an organization near you to get involved!

Read more about the other lakes in the Yahara Watershed

Here’s how Lake Kegonsa faired in previous years: