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.

Lake Kegonsa by the numbers

Lake Kegonsa Watershed
Lake Kegonsa 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

How was the water?

In 2018, summer water clarity conditions show great improvement over the past decade median levels. Total phosphorus levels were “fair” but clarity conditions were “good” in the middle of the lake, according to Wisconsin DNR criteria.

Water clarity (2018 data)

  • 4.6 feet or “good” according to Department of Natural Resources criteria for shallow lakes
Lake Kegonsa 2018 Median Clarity Chart
Source Dr. R. Lathrop, UW Center for Limnology
Data WDNR (1975-1994), NTL-LTER (1995-2018)

Phosphorus levels (2018 data)

  • 0.089 mg/L or “fair” according to Department of Natural Resources criteria for shallow lakes
Lake Kegonsa 2018 Median Phosphorus Chart
Source Dr. R. Lathrop, UW Center for Limnology
Data WDNR (1975-1994), NTL-LTER (1995-2018)

Beaches (2018 data)

The middle of the lake water quality conditions are a contrast to reports of 25 cyanobacteria blooms in the nearshore. This was well above the 4-year median of 2.5. An increase in cyanobacteria blooms have been linked to the invasion of zebra mussels in other lakes systems.

What’s new on the lake?

Kegonsa saw improved water clarity in 2018. This improved clarity could be due to the removal of carp from the lake in recent years, the carp die-off from the koi virus in September 2017, and/or the recent infestation of zebra mussels. Other possible factors include the unusual amount of flow into and out of the lake due to above normal precipitation in the region.

Lake Kegonsa Cyanobacteria, September 2018
Lake Kegonsa State Park Beach – cyanobacteria bloom spotted after the August 2018 flooding

2018 Lake Kegonsa projects

  • Wisconsin Department of Natural Resources, through the Rough and Detrimental Fish Removal Program, contracted anglers to remove close to 100,000 pounds of carp. This action will reduce resuspension and internal loading of phosphorus from the lake sediments into the water column. The Wisconsin DNR estimates 5,552 pounds of phosphorus reduction per year of internal loading within the lake as a result of the removal.
  • Dane County installed more than six miles of buffers in Door Creek through the Harvestable Buffer Program.
  • Town of Dunn* enhanced their leaf collection program with $30,000 from Yahara WINS. The town bought a leaf vacuum, increased the frequency of collection, and expanded collection from 409 to 800 homes.
  • Town of Pleasant Springs* enhanced their leaf collection program (started in 2017) with a leaf vacuum service and leaf drop-off site. They also extended compost site hours and days.
  • Friends of Lake Kegonsa Society* worked with Wisconsin DNR on the carp removal project. Incentive payments were offered to anglers. The partners worked with the Town of Dunn and Town of Pleasant Springs to enhance leaf collection in both towns.
  • City of Stoughton put in stormwater projects at Stoughton Public Works Facility, Kettle Park Senior Living, Edge One Addition, and Grosso Storage Building.

*Denotes a project partially funded by Clean Lakes Grants.

FOLKS Leaf Vacuum, 2018
Friends of Lake Kegonsa Society worked with the Town of Dunn and the Town of Pleasant Springs to enhance leaf collection around Lake Kegonsa

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: