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Rock Lake
Enhanced dataInteractive depth contours
Rock LakeJefferson County, WI
Contours load with map Access
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 80% of the lake. Small gaps between recordings are smoothly connected; larger unrecorded areas follow the lake's depth model calibrated to the DNR-documented 60-ft maximum depth. More accurate than a pure model, but still an estimate. Not for navigation.LakeList assistant
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Fishing spots, food, lodging, marinas, and rentals around Rock Lake.
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Fishing forecast
Best windows for Rock Lake
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
Rock Lake 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.
DNR water check
Water quality quick take
From Wisconsin DNR / Citizen Lake Monitoring readings at Rock Lake - Deep Hole.
Sampled Jun 2026Volunteer monitoring since 1988
Clear, low-algae water — summer clarity of 12.3 ft is lower than most monitored Wisconsin lakes.
Based on July–August 2025 averages across 8 volunteer readings.41Mesotrophic5-yr summer TSI
Moderately clear with moderate nutrients — a typical profile for good swimming lakes.
Water claritySecchi disk depth
12.3 ftJul–Aug 2025 avg (4 readings)
ClearStable since 2018
Clearer than 44% of 596 monitored Wisconsin lakes with current readings.
AlgaeChlorophyll-a
3.3 µg/LJul–Aug 2025 avg (4 readings)
LowStable since 2018
NutrientsTotal phosphorus — fuels plant & algae growth
14 µg/LLatest single sample · 2025-05-23
LowLow phosphorus means light plant/algae growth pressure.
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 | 12.3 ft (4) | 3.3 µg/L (4) | — |
| 2024 | 17.5 ft (1) | 3.3 µg/L (3) | — |
| 2023 | 13.2 ft (2) | 2.5 µg/L (2) | — |
| 2022 | 11.7 ft (3) | 3.5 µg/L (2) | — |
| 2021 | 12.0 ft (2) | 3.5 µg/L (2) | — |
| 2020 | 14.0 ft (2) | 2.5 µg/L (2) | — |
| 2019 | 11.4 ft (4) | 4.3 µg/L (4) | — |
| 2018 | 9.6 ft (5) | 3.8 µg/L (5) | — |
| 2017 | 13.2 ft (4) | 3.4 µg/L (5) | — |
| 2016 | 12.4 ft (2) | 3.0 µg/L (2) | — |
Latest individual samples: Secchi 8 ft (2026-06-22), chlorophyll-a 2 µg/L (2026-06-22), and total phosphorus 14 µg/L (2025-05-23).
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.
Rock Lake - Deep HoleStation 283123 · TSI based on chlorophyll
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 maps2 converted map sheetsView 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
Rock Lake depth maps
2 converted map sheets. These historical surveys are not for navigation.
Navigable depth map
Rock Lake · 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 830700 · 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.
Wisconsin DNR fisheries survey
Fish population survey
Structured LakeList extraction from the 2022 DNR fisheries survey. Population estimates, density, and catch-rate indices use different units, methods, and scopes, so each value is presented in its original form rather than normalized against a different measure.
Survey indicatorsValues keep their source unit and method; unlike measures are not scaled or compared.
Management contextThe report is specific to Rock Lake and combines 112 SNI net-nights, a 7.48-mile SEI walleye recapture run, eight SEII bass miles with two all-species miles, and a 6.53-mile fall walleye transect. Each metric retains its gear-specific scope.
The 2022 comprehensive survey found very high stocked walleye catch rates but only one estimated adult per acre, abundant naturally reproducing northern pike, moderate largemouth bass, small bluegill size structure, declining black crappie size structure, and low yellow perch abundance.
- The walleye estimate remained below the 1.5-adult-per-acre target for stocked lakes, and DNR recommended continued alternate odd-year stocking plus natural-reproduction studies.
- The report cautions that standard protocols do not sample black crappie or yellow perch effectively in Rock Lake.
Black crappie
172 fishBlack crappie captured · p. 131.5 fish/net-nightBlack crappie CPUE · p. 133.4 inchesMinimum black crappie length · p. 1313.4 inchesMaximum black crappie length · p. 13
Bluegill
357 fishBluegill captured · p. 12178.5 fish/mileBluegill CPUE · p. 121.5 inchesMinimum bluegill length · p. 129.2 inchesMaximum bluegill length · p. 12
Common carp
4 fishCommon carp captured · p. 152 fish/mileCommon carp CPUE · p. 15
Largemouth bass
197 fishLargemouth bass captured · p. 1224.6 fish/mileLargemouth bass CPUE · p. 120.7 inchesMinimum largemouth bass length · p. 1215.6 inchesMaximum largemouth bass length · p. 12
Northern pike
458 fishNorthern pike captured · p. 104.1 fish/net-nightNorthern pike CPUE · p. 109.2 inchesMinimum northern pike length · p. 1035.3 inchesMaximum northern pike length · p. 10
Pumpkinseed
34 fishPumpkinseed captured · p. 1417 fish/milePumpkinseed CPUE · p. 1456 percentPumpkinseed PSD · p. 14
Rock bass
35 fishRock bass captured · p. 1417.5 fish/mileRock bass CPUE · p. 1432 percentRock bass PSD · p. 146 percentRock bass PSD-P · p. 14
Walleye
1,622 fishWalleye captured · p. 914.5 fish/net-nightWalleye CPUE · p. 913.4 inchesMinimum walleye length · p. 925.9 inchesMaximum walleye length · p. 9
Yellow perch
9 fishYellow perch captured in SNI · p. 140.1 fish/net-nightYellow perch SNI CPUE · p. 145.6 inchesMinimum SNI yellow perch length · p. 148 inchesMaximum SNI yellow perch length · p. 14
Rock Lake comprehensive survey, 2022Matched by exact lakelist id name county state wbic · WBICs 830700 · verified 2026-07-19Wisconsin DNR fisheries survey report; LakeList operator documented permission to leverage this report with source attribution.
1,365surface acres
60max depth feet
5public access points
43.0772, -88.9316latitude, longitude
Access
Public access points
Boat launchElm Point Rock Lake Access43.06981, -88.93779Managed by Wisconsin DNR
DNR verifiedDirections
Boat launchFerry Park Landing43.08854, -88.93540Managed by TOWNSHIPTOWN OF LAKE MILLSRamp surface: GravelADA-accessible feature: NoVerified 2026-07-12
Boat launchNorth End Launch Park Lane Rd43.09539, -88.92921Managed by Wisconsin DNR
DNR verifiedDirections
Boat launchRock Lake Carry In Access43.09630, -88.93288Managed by Select One...Select One...Ramp surface: ConcreteLanding type: CARRY-INADA-accessible feature: NoVerified 2026-07-12
Boat launchSandy Beach Boat Ramp43.06672, -88.92454Managed by CITYCITY OF LAKE MILLSRamp surface: ConcreteADA-accessible feature: YesVerified 2026-07-12
Nearby
Trip-planning places
No nearby trip-planning places yet
Fishery
Notable species
Largemouth BassPanfishSmallmouth BassWalleyeNorthern Pike
Depth FAQ
How deep is Rock Lake?
Rock Lake is 60 feet deep at its deepest point and averages about 16 feet, according to Wisconsin DNR records.
Is there a free depth map of Rock Lake?
Yes. LakeList publishes a free interactive depth contour map of Rock Lake 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 Rock Lake 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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