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Lake Monona
Enhanced dataInteractive depth contours
Lake MononaDane County, WI
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Interactive depth contours5-foot typical interval · Sonar-derived depth (C-MAP Genesis) · Gaps interpolated · Not for navigation
Source: C-MAP Genesis community sonar (derived)high confidence · QA passed · Select a contour to inspect its mapped depthDepths decoded from C-MAP Genesis Social Map community sonar recordings (used with permission), covering 97% of the lake. Small gaps between recordings are smoothly connected; larger unrecorded areas follow the lake's depth model calibrated to the DNR-documented 74-ft maximum depth. More accurate than a pure model, but still an estimate. Not for navigation.LakeList assistant
Plan your lake day
Fishing spots, food, lodging, marinas, and rentals around Lake Monona.
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Fishing forecast
Best windows for Lake Monona
Weather-based planning built from the National Weather Service hourly forecast near this lake.
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Checking wind, precipitation, and near-term weather windows.
Water temperature
Lake Monona water temperature today
Modeled surface-temperature estimate built from seasonal climate, lake depth, and live National Weather Service air temperatures near this lake.
74°FWarm
Seasonal estimate. Checking current National Weather Service air temperatures…
Comfortable summer pattern. Bass and panfish are active; early and late hours beat the midday heat.
Estimates are modeled, not measured. Actual temperatures vary with depth, wind mixing, and recent weather — verify conditions before swimming, boating, or heading onto ice.
Wisconsin DNR water assessment
Public-health advice and impairment listed
The DNR assessment indicates specific public-health advice for this waterbody. Review current official guidance before your trip or eating your catch.
303(d) / impairment recordSpecific public-health adviceRecreation restrictions noted
Human Health Risks - Toxics, PCBs Contaminated Fish Tissue, Excess Algal Growth, Eutrophication, PCB Contaminated Sediments, PFOS Contaminated Fish TissuePollutants: Mercury, PFOS, Total Phosphorus, PCBs
- Status
- TMDL Approved, 303d Listed, Pollutant Removed
- Public health
- Specific Advice
- Recreation
- Recreational Restrictions
- Aquatic life
- Not specified
Water is impaired due to one or more pollutants and associated quality impacts.
Review DNR water quality Check consumption advice Source updated 2026-03-25 · LakeList verified 2026-07-12
DNR water check
Water quality quick take
From Wisconsin DNR / Citizen Lake Monitoring readings at Lake Monona - Deep Hole.
Sampled Jun 2026Volunteer monitoring since 1989
Somewhat hazy water — summer clarity of 3.9 ft sits near the middle of monitored Wisconsin lakes.
Based on July–August volunteer averages from 2022–2024; each value shows its own year.55Eutrophic5-yr summer TSI
Nutrient-rich, greener water — more algae and plant growth, common in shallower lakes.
Water claritySecchi disk depth
3.9 ftJul–Aug 2024 avg (5 readings)
HazyImproving — up ~29% vs earlier years
Clearer than 49% of 596 monitored Wisconsin lakes with current readings.
AlgaeChlorophyll-a
10.5 µg/LJul–Aug 2022 avg (2 readings)
ElevatedImproving — down ~18% vs earlier years
No recent nutrient readings — last measured 2019.
Listed as impaired on the DNR/EPA water-condition assessment — see the notice on this page for details.All readings by year · station details · methodology
Summer averages (July/August)
July/August means; counts in parentheses show how many samples went into each average.
| Year | Secchi | Chlorophyll-a | Total phosphorus |
|---|---|---|---|
| 2025 | — | — | — |
| 2024 | 3.9 ft (5) | 20.0 µg/L (1) | 106.0 µg/L (1) |
| 2023 | 6.8 ft (4) | 5.0 µg/L (1) | — |
| 2022 | 6.4 ft (8) | 10.5 µg/L (2) | — |
| 2021 | 4.3 ft (5) | — | — |
| 2019 | — | — | 42.0 µg/L (2) |
| 2018 | 4.5 ft (1) | — | — |
| 2017 | 4.5 ft (1) | — | — |
| 2016 | 5.2 ft (5) | 15.0 µg/L (1) | — |
| 2015 | — | 14.0 µg/L (1) | — |
Latest individual samples: Secchi 8.3 ft (2026-06-25), chlorophyll-a 2 µg/L (2025-05-22), and total phosphorus 88 µg/L (2025-11-20).
Secchi clarity is how deep a black-and-white disk stays visible from the surface — more feet means clearer water.
Chlorophyll-a is an algae pigment; higher values signal more algae in the water column.
Total phosphorus is a nutrient that feeds algae and aquatic plants. It is not a weed survey — depth, bottom type, water movement, and management change the actual lake experience.
Lake Monona - Deep HoleStation 208 · TSI based on Secchi
Modeled from DNR/CLMN monitoring — not a safety or swim-condition report. Verify current conditions locally. LakeList verified 2026-07-12.Official Wisconsin information
Plan with DNR sources
LakeList links to the authoritative record so you can verify maps, rules, and current notices before leaving.
Historical DNR depth maps1 converted map sheetView DNR depth mapHistorical map · not for navigationFishing regulationsVerify current seasons, limits, and restrictionsOfficial DNR lake pageFacts, advisories, boating, and water qualityWater quality reportsMonitoring stations, clarity, and DNR reportsInvasive speciesVerified, observed, and historical AIS recordsBoating ordinancesLocal slow-no-wake and water-use restrictionsFish consumption advisoriesStatewide and waterbody-specific health guidance
Historical depth maps are not for navigation. Verify regulations and access at the official source before your trip.
Historical Wisconsin DNR maps
Lake Monona depth maps
1 converted map sheet. These historical surveys are not for navigation.
Navigable depth map
Lake Monona · sheet 1
Pan, zoom, and inspect the converted Wisconsin DNR historical map image in the browser. Historical survey — not for navigation.
Source: Wisconsin DNR · WBIC 804600 · image navigation only; spatial alignment pending · Historical lake maps are not for navigation.
Source: Wisconsin Department of Natural Resources. Converted for browser access with source URLs, checksums, and retrieval dates retained. Historical lake maps are not for navigation.
3,359surface acres
74max depth feet
5public access points
43.0677, -89.3642latitude, longitude
Access
Public access points
Boat launchAccess - Off Willy/Blair St43.07535, -89.37500Managed by Wisconsin DNR
DNR verifiedDirections
Boat launchOlbrich Park Access43.08721, -89.33011Managed by Wisconsin DNR
DNR verifiedDirections
Boat launchOlin Park Access43.05555, -89.37740Managed by Wisconsin DNR
DNR verifiedDirections
Boat launchTonyawatha Park Boat Ramp43.07185, -89.33762Managed by Wisconsin DNR
DNR verifiedDirections
Boat launchWinnequah Trail Boat Ramp43.05632, -89.34963Managed by CITYCITY OF MADISONRamp surface: ConcreteADA-accessible feature: YesVerified 2026-07-12
Nearby
Trip-planning places
No nearby trip-planning places yet
Fishery
Notable species
PanfishLargemouth BassNorthern PikeWalleyeCatfishMuskySmallmouth BassSturgeon
Depth FAQ
How deep is Lake Monona?
Lake Monona is 74 feet deep at its deepest point and averages about 27 feet, according to Wisconsin DNR records.
Is there a free depth map of Lake Monona?
Yes. LakeList publishes a free interactive depth contour map of Lake Monona at a typical 5-foot interval, with an optional 3D underwater view, derived from C-MAP Genesis community sonar (derived) survey data.
Where does the Lake Monona depth map come from?
The interactive depth contours are derived from C-MAP Genesis community sonar (derived). Each contour set passes a visual QA review against the source document before it is published. The depths are derived from community sonar recordings (C-MAP Genesis Social Map, used with permission), with gaps between recordings interpolated; not for navigation.
Trust and freshness
Where this lake data comes from
Wisconsin DNR Lake Mapsname, coordinates, county, source identifiers
LakeList record updated 2026-07-14
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