LakeList
FavoritesStateWisconsin
Big Portage Lake
Enhanced dataInteractive depth contours
Big Portage LakeVilas County, WI
Contours load with map Access
Interactive depth contours5-foot typical interval · Modeled depth estimate · Not a survey · Not for navigation
Source: LakeList depth modelmedium confidence · QA passed · Select a contour to inspect its mapped depthModeled depth estimate: contours computed from the lake's shoreline shape and its documented 40-ft maximum depth (depth grows with distance from shore, calibrated to the documented mean depth where available). This is a smooth mathematical model, not a survey - real holes, bars, and drop-offs will differ. Community sonar (C-MAP Genesis) overlays where recorded. Not for navigation.LakeList assistant
Plan your lake day
Fishing spots, food, lodging, marinas, and rentals around Big Portage Lake.
Start here
Fishing forecast
Best windows for Big Portage Lake
Weather-based planning built from the National Weather Service hourly forecast near this lake.
Loading latest forecast…
Checking wind, precipitation, and near-term weather windows.
Water temperature
Big Portage 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 Big Portage Lake - Deep Hole.
Sampled May 2026Volunteer monitoring since 1991
Very clear, low-algae water — summer clarity of 17.8 ft puts it among the clearest tenth of monitored Wisconsin lakes.
Based on July–August 2024 averages across 7 volunteer readings.40Oligotrophic5-yr summer TSI
Very clear, low-nutrient water — often deep, with limited plant growth.
Water claritySecchi disk depth
17.8 ftJul–Aug 2024 avg (4 readings)
Crystal clearStable since 2018
Clearer than 96% of 596 monitored Wisconsin lakes with current readings.
AlgaeChlorophyll-a
2.7 µg/LJul–Aug 2024 avg (3 readings)
LowStable since 2018
No recent nutrient readings — last measured 2020.
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 | 23.0 ft (1) | 1.0 µg/L (1) | — |
| 2024 | 17.8 ft (4) | 2.7 µg/L (3) | — |
| 2023 | 22.5 ft (4) | 2.7 µg/L (3) | — |
| 2022 | 17.9 ft (5) | 3.0 µg/L (3) | — |
| 2021 | 20.1 ft (4) | 2.0 µg/L (3) | — |
| 2020 | 18.5 ft (5) | 2.3 µg/L (3) | 11.0 µg/L (1) |
| 2019 | 18.5 ft (4) | 2.5 µg/L (2) | — |
| 2018 | 20.2 ft (5) | 1.5 µg/L (2) | — |
| 2017 | — | 2.0 µg/L (2) | — |
| 2016 | 17.5 ft (2) | 3.0 µg/L (2) | — |
Latest individual samples: Secchi 21.5 ft (2026-05-29), chlorophyll-a 5 µg/L (2025-09-03), and total phosphorus 11 µg/L (2020-07-01).
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.
Big Portage Lake - Deep HoleStation 643165 · 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 maps1 converted map sheetFishing 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
Big Portage Lake depth maps
1 converted map sheet. These historical surveys are not for navigation.
Navigable depth map
Big Portage 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 1629500 · 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.
586surface acres
40max depth feet
1public access points
46.1256, -89.2849latitude, longitude
Access
Public access points
Boat launchBig Portage Lake Access46.11619, -89.28433Managed by TOWNSHIPTOWN OF LAND O LAKESRamp surface: ConcreteADA-accessible feature: NoVerified 2026-07-12
Nearby
Trip-planning places
No nearby trip-planning places yet
Fishery
Notable species
Smallmouth BassWalleyeLargemouth BassPanfish
Depth FAQ
How deep is Big Portage Lake?
Big Portage Lake is 40 feet deep at its deepest point and averages about 18 feet, according to Wisconsin DNR records.
Is there a free depth map of Big Portage Lake?
Yes. LakeList publishes a free interactive depth contour map of Big Portage Lake at a typical 5-foot interval, with an optional 3D underwater view, derived from LakeList depth model survey data.
Where does the Big Portage Lake depth map come from?
The interactive depth contours are derived from LakeList depth model. Each contour set passes a visual QA review against the source document before it is published. The depths are a modeled estimate calibrated to the lake's documented maximum depth - not a survey, and not for navigation.
Trust and freshness
Where this lake data comes from
Wisconsin DNR Lake Pagesname, coordinates, county, source identifiers
LakeList record updated 2026-05-25