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LakeQuality
A

Long Lake

Washburn County, WisconsinOligotrophic

On the LakeGrade rubric, Long Lake pulls an A: clarity at 29.5 ft and 18 µg/L of phosphorus put it in the top bracket for Wisconsin. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. 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 48 graded lakes in Washburn County, Long Lake ranks 1 — in the top quartile locally.

Long Lake has no invasive species recorded in Wisconsin state databases as of 2025, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Long 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 2025-08-25. 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 29.5 ft down. Phosphorus level: 17.5 µg/L. Trophic State Index: 37.

MetricValueGrade
Water Clarity (Secchi Depth)29.5 ftA
Phosphorus17.5 µg/LA
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)37Oligotrophic

Low nutrients, clear water, excellent for swimming

Location

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County Ranking

Ranked #1 of 48 lakes in Washburn County

Nearby Lakes in Washburn County

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Most recent sample: 2025-08-25

Monitoring stations: 6