Lake Kegonsa
Lake Kegonsa in Dane County, Wisconsin has a water quality grade of D (Nutrient-rich). Water clarity: 3.7 ft visibility. Phosphorus: 59.5 µg/L. Maximum depth: 32 ft. Surface area: 3200 acres.
- Clarity
- 3.7 ft
- Typical in August
- 79°F
- Max depth
- 32 ft
- Area
- 3,200 acres
- Type
- Eutrophic
- Trend
- → Stable
- Public access
- Yes
Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Lake Kegonsa →
Next lake in Dane County
Lake Kegonsa is a 3,200-acre productive, nutrient-rich eutrophic lake in Dane County, Wisconsin with a maximum depth of 32 feet. Water quality is graded D based on 1 sampling years through 2026. Water clarity is declining over recent sampling years. The lake supports 7 documented fish species including Musky, Panfish, and Largemouth Bass. Public access is available with 4 public boat landings. Compared to the 14 other monitored lakes in Dane County, Lake Kegonsa ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-04-10. Grade methodology: LakeGrade methodology.
Watch Lake Kegonsa water quality
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Lake Kegonsa Water Quality Report Card (2026)
A printable one-page report card for Lake Kegonsa: grade, clarity, phosphorus, algae, multi-year trend, depth, and fish — with sources.
Swimming Safety
Grade onlyBacteria D
Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Based on E. coli testing, Lake Kegonsa frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 10.1% of 473 samples across 9 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Wisconsin’s current beach and health-department advisories before swimming.
Water Quality Grade: D (Nutrient-rich)
Murky, only visible to about 3.7 ft. Phosphorus level: 59.5 µg/L. Trophic State Index: 61.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.7 ft | Not graded |
| Phosphorus | 59.5 µg/L | Poor |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 61 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake Kegonsa
Compare lakeside cabins, hotels, and vacation rentals near Lake Kegonsa in Dane County, Wisconsin — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Lake Kegonsa are listed below.
Top-rated places to stay near Lake Kegonsa
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Planning a trip? Cabins and lodging at Lake Kegonsa → · more Wisconsin lake trips
Current Conditions
USGS snapshot Jul 6, 2026, 5:00 AM from gauge 425715089164700 (Lake Kegonsa at Barber Drive Near Stoughton, WI). Station page ↗ — a live reading replaces this snapshot when the gauge responds. Missing live data is not an all-clear.
Water Temperature
Lake Kegonsa typically sits around 79°F at the surface in August. Summer average is about 78°F. Usually warmest in Jul (about 80°F) and coldest in May (about 62°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 48 field readings (2024–2025) via the EPA Water Quality Portal. See the full Lake Kegonsa water temperature breakdown →
Blue-Green Algae (Cyanobacteria)
There’s no recent EPA CyAN cyanobacteria estimate for Lake Kegonsa — clouds, ice, or an off-season gap in coverage. The most recent reading was high (205,116 cells/mL) on July 18, 2026.
Blue-green algae can appear and clear within days, so check your state’s current advisory before swimming. EPA CyAN ↗
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 32 ft |
| Surface Area | 3,200 acres |
| Public Access | Yes |
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Pleasant SpringsPublic
- Fish Camp County ParkPublic
- Lake Kegonsa State ParkPublic
- South Quam DrivePublic
Fish Species
Click a species to see every graded lake where it is documented.
Fishing Lake Kegonsa
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. Monitored by volunteers since 1989. 18 stations on file (most recent sample 2026).
Fish Species (DNR-rated)
DNR Reports & Resources
Wisconsin DNR Fisheries scientists publish multi-year survey reports for Lake Kegonsa covering fish populations, stocking, water quality, and management. 1 report on file.
These links open on the official state DNR websites (Wisconsin DNR survey PDFs · Minnesota DNR LakeFinder).
- 2016Lake Kegonsa comprehensive survey, 2016Comprehensive Survey · WI DNR · 2016 (PDF)
Water Quality Trend: → Stable
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.188 m/yr | 6 |
| Phosphorus | ↑ Improving | -5.44 µg/L/yr | 4 |
Reservoir Info (USACE NID)
Lake Kegonsa is a man-made reservoir impounded by the Lake Kegonsa (completed 1938), built primarily for navigation on the YAHARA; gravity-type dam, 10 ft tall and 100 ft long.
- Surface area
- 2,716 ac
- Normal storage
- 2,716 ac-ft
- Max storage
- 16,300 ac-ft
- Drainage area
- 410 sq mi
- Hazard class
- Low
- Owner
- Dane County
All listed purposes: Navigation;Recreation.
Source: USACE National Inventory of Dams, NID ID WI01072 · Operator website
EPA Impairment Status
Lake Kegonsa is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit WI10027603 · Official waterbody report
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Lake Kegonsa under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 1 facility has a reported Clean Water Act violation in the past three years.
- Stoughton Wastewater Treatment FacilityStoughton · 5 mi away · NPDES WI0020338MajorRecent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
County Ranking
Ranked #6 of 15 lakes in Dane County
Nearby Lakes With Higher Grades
Lake Kegonsa holds Grade D. 3 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
See full comparison →Nearby Lakes in Dane County
Frequently asked questions about Lake Kegonsa
What is the water quality grade for Lake Kegonsa?
- Lake Kegonsa in Dane County, Wisconsin has a water quality grade of D (Nutrient-rich). Water clarity: 3.7 ft visibility. Phosphorus: 59.5 µg/L. Maximum depth: 32 ft. Surface area: 3200 acres.
Is Lake Kegonsa safe to swim in?
- Based on E. coli testing, Lake Kegonsa frequently exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 10.1% of 473 samples across 9 seasons. That works out to a bacteria swim-safety grade of D — a historical summary of past testing, not a current reading. Lake Kegonsa has a water quality grade of D (Nutrient-rich). Bacteria levels can spike quickly after heavy rain, so always check Wisconsin's current beach and health-department advisories before you swim.
What is the water temperature of Lake Kegonsa?
- Lake Kegonsa typically sits around 79°F at the surface in August, from 48 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading.
How deep is Lake Kegonsa?
- Lake Kegonsa has a maximum depth of 32 feet. The lake covers 3200 acres.
What fish are in Lake Kegonsa?
- Fish species found in Lake Kegonsa include Musky, Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye, Catfish. Lake Kegonsa is located in Dane County, Wisconsin.
What is the water level at Lake Kegonsa?
- The USGS snapshot on this page for Lake Kegonsa is 843.29 ft of water-surface elevation, recorded Jul 6, 2026, 5:00 AM at gauge 425715089164700. Current Conditions hydrates a live NWIS reading from that same station when the gauge responds. A missed live fetch is not an all-clear.
Does Lake Kegonsa have blue-green algae?
- There is no recent EPA CyAN cyanobacteria estimate for Lake Kegonsa (clouds, ice, or an off-season gap). The most recent reading was high (205,116 cells/mL). Blue-green algae can appear and clear within days, so check Wisconsin's current advisory before swimming.
Are there boat ramps on Lake Kegonsa?
- Lake Kegonsa has 4 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Pleasant Springs, Fish Camp County Park, Lake Kegonsa State Park, South Quam Drive. Public access is listed as yes.
Explore Lake Kegonsa across LakeGrade
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Where this data comes from
102 measurements from 1 monitoring station, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX102 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (1)
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Fish and recreation data from Wisconsin DNR Lakes
Named boat-access points from the USGS National Boat Ramps inventory