Skip to main content
LakeQuality
A

Nelson Lake

Sawyer County, WisconsinMesotrophic

Nelson 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.

A TSI near 44 places Nelson Lake in the mesotrophic band — moderate productivity, with seasonal swings between clearer spring water and richer late-summer conditions. 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. Nelson Lake sits at rank 35 of 52 in Sawyer County, in the lower half of the local distribution.

No invasive species are currently listed at Nelson Lake — the lake remains off the Wisconsin infested-waters roster. The state fisheries records do not list documented species for Nelson 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 2025-10-27. Grade methodology: LakeGrade methodology.

Swimming Safety

Excellent for swimming, crystal clear water with minimal algae

Water Quality Grade: A, Excellent

Crystal clear, you can see 15.2 ft down. Phosphorus level: 23.9 µg/L. Trophic State Index: 44.

MetricValueGrade
Water Clarity (Secchi Depth)15.2 ftA
Phosphorus23.9 µg/LB
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)44Mesotrophic

Moderate nutrients, good water quality

Water Quality Trend: Stable

Based on 7 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Stable-0.054 m/yr7
See year-by-year chart →

Location

Loading map…

County Ranking

Ranked #35 of 52 lakes in Sawyer County

Nearby Lakes in Sawyer County

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Most recent sample: 2025-10-27

Monitoring stations: 3