Lake Monona
Dane County, WisconsinView mapDirections
Wisconsin DNR publishes the water-quality measurements for Lake Monona. Here is what has been measured.
- Eutrophic
- 70 ft max depth
- Public access
Lake Monona in Dane County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 7 ft visibility. Phosphorus: 98.5 µg/L.
Lake Monona is a productive, nutrient-rich eutrophic lake in Dane County, Wisconsin with an estimated average depth of about 70 feet. Water clarity is improving over recent sampling years. Limited fish-species data available. Public access is available with 5 public boat landings. Compared to the 14 other monitored lakes in Dane County, Lake Monona ranks #8 for water quality.
Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-06-25. Methodology: how these readings are compared.
Lake Monona has 5 public boat landings, so a lakefront rental is not the only way to get a boat on the water. For a place on the water, look through cabin and lake-house rentals near Lake Monona on Vrbo. For a hotel or motel room, Booking.com and Expedia both search around the lake.
What Lake Monona is good for
From access and monitoring records, not editorial picks.
- Boat launch5 documented ramps
Lake Monona Water Quality Summary (2026)
A printable one-page summary for Lake Monona: clarity, phosphorus, algae, multi-year trend, depth, and fish — with sources.
Swimming conditions
Readings onlyElevated nutrients
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. Check local advisories before you swim.
Whether Lake Monona 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 Monona
These are the measurements Wisconsin DNR publishes for Lake Monona, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 7 ft. Phosphorus 98.5 µg/L. TSI 60.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 7ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 98.5µg/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. | 60 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Lake Monona
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 05429000 (Lake Monona at Madison, WI). Station page ↗ — a live reading replaces this snapshot when the gauge responds. Missing live data is not an all-clear.
Water Temperature
Lake Monona typically sits around 76°F at the surface in August. Summer average is about 77°F. Usually warmest in Jul (about 78°F) and coldest in Jun (about 76°F). These are typical values by month — see Current Conditions above for the latest gauge reading.
Column height runs from this lake’s coldest month (76°F) to its warmest (78°F).
Typical surface water temperature by month, from 18 field readings (2024–2025) via the EPA Water Quality Portal. See the full Lake Monona water temperature breakdown →
Lake Details
Max depth
~70 ft est.
Public access
Yes
Listed by Wisconsin DNR
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Wisconsin has not published bathymetry for Lake Monona.
Lake Size & Watershed
Watershed (drainage) area
281 sq mi
HydroLAKES / HydroSHEDS
Surface area
3,291 acres
HydroLAKES / HydroSHEDS
Shoreline
13 mi
HydroLAKES / HydroSHEDS
Elevation
840 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- Olbrich ParkPublic
- Tonyawatha ParkPublic
- Lottes ParkPublic
- Burr Jones ParkPublic
- Winnequah TrailPublic
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 Monona
Compare lakeside cabins, hotels, and vacation rentals near Lake Monona 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 Monona are listed below.
Top-rated places to stay near Lake Monona
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 Monona → · more Wisconsin lake trips
Follow Lake Monona’s readings
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Fishing Lake Monona
Water Quality Trend: Stable
Based on 7 years of monitoring (2020–2026).
Water clarity
Improving6 years
Phosphorus
Worsening+11.04 µg/L/yr7 years
Regulated Pollution Sources Nearby
2 EPA-permitted facilities operate within about 5 miles of Lake Monona under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 2 facilities have a reported Clean Water Act violation in the past three years.
- Madison Metro Sew Dist WwtfMadison · 1.8 mi away · NPDES WI0024597MajorRecent violation
- Madison Gas & Electric Blount StationMadison · 0.9 mi away · NPDES WI0001961Recent 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.
Nearby Lakes in Dane County
Frequently asked questions about Lake Monona
Where is Lake Monona?
- Lake Monona 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 Monona?
- Lake Monona in Dane County, Wisconsin has water-quality measurements published by Wisconsin DNR, shown here as reported. Water clarity: 7 ft visibility. Phosphorus: 98.5 µg/L.
Is Lake Monona safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Lake Monona?
- Lake Monona typically sits around 76°F at the surface in August, from 18 EPA Water Quality Portal field readings (2024–2025). That is a typical value for the month, not a live reading. A USGS gauge on this lake last read 78°F.
How deep is Lake Monona?
- No published bathymetric survey covers Lake Monona, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 70 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
What is the water level at Lake Monona?
- The USGS snapshot on this page for Lake Monona is 845.04 ft of water-surface elevation, recorded Jul 6, 2026, 5:00 AM at gauge 05429000. 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 Monona?
- Lake Monona has 5 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Olbrich Park, Tonyawatha Park, Lottes Park, Burr Jones Park, among others. Public access is listed as yes.
Can I fish at Lake Monona?
- Lake Monona has 5 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 Monona across LakeQuality
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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
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Where this data comes from
321 measurements from 2 monitoring stations, 2020–2026. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Wisconsin Department of Natural Resources
WIDNR_WQX321 samples · 2020–2026
Analytical methods
- Phosphorus by Colorimetry
Monitoring station identifiers (2)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory