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LakeQuality
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North Twin Lake

Washburn County, WisconsinOligotrophic

On the LakeGrade rubric, North Twin Lake pulls an A: clarity at 29.5 ft and 14 µg/L of phosphorus put it in the top bracket for Wisconsin. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

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. North Twin Lake ranks 15 of 48 in Washburn County — solidly in the upper half of the local distribution.

North Twin 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 North Twin 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 2025-08-31. 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: 13.7 µg/L. Trophic State Index: 35.

MetricValueGrade
Water Clarity (Secchi Depth)29.5 ftA
Phosphorus13.7 µg/LA
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)35Oligotrophic

Low nutrients, clear water, excellent for swimming

Water Quality Trend: Improving

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

MetricTrendChange/YearYears
Water Clarity Improving+0.346 m/yr7
Phosphorus Stable+0.03 µg/L/yr6
See year-by-year chart →

Location

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County Ranking

Ranked #15 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: 2025-08-31

Monitoring stations: 1