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Big Lake

Vilas County, WisconsinMesotrophic

Big Lake sits at the top of the Wisconsin DNR grading rubric with an A, a mark reached by the cleanest lakes in Wisconsin. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

The lake sits in the mesotrophic zone — the band where most well-managed Wisconsin lakes fall. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Among the 191 graded lakes in Vilas County, Big Lake sits at rank 59, above the county median.

No invasive species are currently listed at Big Lake — the lake remains off the Wisconsin infested-waters roster. The state fisheries records do not list documented species for Big Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.

Source: EPA Water Quality Portal sampling records, Wisconsin DNR Surface Water, last sampled 2026-05-07. Grade methodology: LakeGrade methodology.

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Swimming Safety

Excellent for swimming, crystal clear water with minimal algae

Water Quality Grade: A, Excellent

Good clarity, visible to about 12 ft. Phosphorus level: 12.8 µg/L. Trophic State Index: 41.

MetricValueGrade
Water Clarity (Secchi Depth)12 ftB
Phosphorus12.8 µg/LA
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)41Mesotrophic

Moderate nutrients, good water quality

Water Quality Trend: Stable

Based on 6 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Stable-0.086 m/yr6
Phosphorus Stable-0.22 µg/L/yr6
See year-by-year chart →

Recreation & Access

12
Boat Landings
Yes
Public Access

Location

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County Ranking

Ranked #59 of 191 lakes in Vilas County

Nearby Lakes in Vilas County

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Public boat-access points from the USGS National Boat Ramps inventory

Most recent sample: 2026-05-07

Monitoring stations: 3

Where to stay near Big Lake

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