Lake Mendota
Dane County, Wisconsin9,781 acresView mapDirections
Wisconsin DNR publishes the water-quality measurements for Lake Mendota. Here is what has been measured.
- Eutrophic
- Impaired · Nutrients (phosphorus, nitrogen)
- 4 aquatic invasives
- 83 ft max depth
- Public access
Lake Mendota in Dane County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 5 ft visibility. Phosphorus: 65.4 µg/L. Maximum depth: 83 ft. Surface area: 9781 acres.
Wisconsin DNR rates Panfish as abundant on Lake Mendota. DNR survey details →
Lake Mendota is a 9,781-acre productive, nutrient-rich eutrophic lake in Dane County, Wisconsin with a maximum depth of 83 feet. Overall water quality is declining over recent sampling years. The lake supports 8 documented fish species including Musky, Panfish, and Largemouth Bass. Public access is available with 9 public boat landings and 7 public beaches. Compared to the 14 other monitored lakes in Dane County, Lake Mendota ranks #9 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-08. Methodology: how these readings are compared.
At about 9,800 acres, Lake Mendota is large enough that where you stay decides which shore you see most of. It has 9 public boat landings, so a lakefront rental is not the only way to get a boat on the water. Vrbo is where to look for cabins and lake homes around Lake Mendota, and Booking.com and Expedia search hotels near the lake for your dates.
What Lake Mendota is good for
From access and monitoring records, not editorial picks.
- Boat launch9 documented ramps
- Beach7 documented beaches
- Fishing8 species recorded
- Deep water83 ft surveyed max depth
- Big water9,781 acres
Lake Mendota Water Quality Summary (2026)
A printable one-page summary for Lake Mendota: clarity, phosphorus, algae, multi-year trend, depth, and fish — with sources.
Swimming conditions
Readings onlyRecreation use not supported
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Lake Mendota is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
Whether Lake Mendota is safe to swim in today is a call for the Wisconsin Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Lake Mendota
These are the measurements Wisconsin DNR publishes for Lake Mendota, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 5 ft. Phosphorus 65.4 µg/L. TSI 59.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 65.4µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 59 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Lake Mendota
Answers come straight from the public measurements and survey records on this page.
Current Conditions
USGS snapshot Jul 6, 2026, 5:00 AM from gauge 05428000 (Lake Mendota at Madison, WI). Station page ↗ — a live reading replaces this snapshot when the gauge responds. Missing live data is not an all-clear.
Wisconsin DNR rates Panfish as abundant on Lake Mendota.
A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Lake Mendota’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
WI DNR Lake Profile
Authoritative data from the Wisconsin DNR LakePages. 12 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 Mendota 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).
- —Lake Mendota gill netting survey, 2020-2024Netting Survey · WI DNR (PDF)
Lake Details
Max depth
83 ft
Surface area
9,781 acres
Public access
Yes
Listed by Wisconsin DNR
Lake Size & Watershed
Watershed (drainage) area
247 sq mi
HydroLAKES / HydroSHEDS
Shoreline
30.6 mi
HydroLAKES / HydroSHEDS
Elevation
846 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS).
Recreation & Access
- Governor Nelson State ParkPublic
- MiddletonPublic
- Mendota County ParkPublic
- Marshall ParkPublic
- Tenney ParkPublic
- Spring Harbor ParkPublic
Showing 6 of 9 documented landings from the USGS National Boat Ramps inventory.
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Stays via Stay22
Stays near Lake Mendota
Compare lakeside cabins, hotels, and vacation rentals near Lake Mendota 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 readings cover nutrients and algae, not lodging. Cabins and rentals around Lake Mendota are listed below.
Top-rated places to stay near Lake Mendota
Prices for Oct 9–11, 4 adults. Change dates on the map below.
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip? Cabins and lodging at Lake Mendota → · more Wisconsin lake trips
Follow Lake Mendota’s readings
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Fish Species
Click a species to see every lake where it is documented.
Fishing Lake Mendota
Invasive & Introduced Species
Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.
Water Quality Trend: Worsening
Based on 7 years of monitoring (2020–2026).
Water clarity
Worsening2 years
Phosphorus
Stable+0.68 µg/L/yr7 years
EPA Impairment Status
Lake Mendota is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit WI6876129 · Official waterbody report
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Lake Mendota under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Wi Dnr Nevin Fish HatcheryFitchburg · 2 mi away · NPDES WI0002585Recent violation
- Uw Madison Charter Street Heating PlantMadison · 2 mi away · NPDES WI0038296Recent violation
- Dane County Regional AirportMadison · 4.3 mi away · NPDES WI0048747
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.
Nearby Lakes in Dane County
Frequently asked questions about Lake Mendota
Where is Lake Mendota?
- Lake Mendota is a lake in Dane County, Wisconsin. Its water-quality measurements are published by Wisconsin DNR and shown on this page as reported.
What is the water quality of Lake Mendota?
- Lake Mendota in Dane County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 5 ft visibility. Phosphorus: 65.4 µg/L. Maximum depth: 83 ft. Surface area: 9781 acres.
Is Lake Mendota safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake Mendota is listed impaired under Clean Water Act §303(d) (IR 4A) for nutrients (phosphorus, nitrogen). Check local advisories before you swim.
How deep is Lake Mendota?
- Lake Mendota has a maximum depth of 83 feet. The lake covers 9781 acres.
What fish are in Lake Mendota?
- Fish species found in Lake Mendota include Musky, Panfish, Largemouth Bass, Smallmouth Bass, Northern Pike, Walleye, Sturgeon, Catfish. Lake Mendota is located in Dane County, Wisconsin.
What did the DNR fisheries survey find at Lake Mendota?
- Wisconsin DNR rates Panfish as abundant on Lake Mendota. A DNR fisheries survey reports fish abundance and catch rates, not water quality. LakeQuality shows Lake Mendota’s water-quality measurements separately, and the water-quality trend over 7 years of monitoring is declining. Catch rate is not a swim clearance and is not a weekly bite report.
What is the water level at Lake Mendota?
- The USGS snapshot on this page for Lake Mendota is 850.06 ft of water-surface elevation, recorded Jul 6, 2026, 5:00 AM at gauge 05428000. Current Conditions hydrates a live NWIS reading from that same station when the gauge responds. A missed live fetch is not an all-clear.
Are there boat ramps on Lake Mendota?
- Lake Mendota has 9 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Governor Nelson State Park, Middleton, Mendota County Park, Marshall Park, among others. Public access is listed as yes.
Can I fish at Lake Mendota?
- Lake Mendota has 9 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Wisconsin's fish and wildlife agency, so check its current regulations before you go.
Explore Lake Mendota across LakeQuality
Depth, room, public access, and the state wake-sport rules
Fish species and the cleanest lakes across Wisconsin
Fish species and best lakes in Dane County
Species activity outlook by water temperature and season
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Where to stay at Wisconsin's top lakes, each with its readings
Lakes in the Wisconsin River Watershed, ranked by water quality
Wisconsin's cleanest lakes, ranked on agency measurements
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Compare Lake Mendota With Nearby Lakes
Where this data comes from
377 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_WQX377 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from 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