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LakeQuality
F

Unnamed Lake

Watonwan County, MinnesotaHypereutrophic

Unnamed Lake earns an F: 275 µg/L of phosphorus and clarity at 1.0 ft signal heavy nutrient loading from the surrounding watershed. 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 hypereutrophic status — TSI 81 — reflects sustained heavy nutrient loading from the surrounding watershed and frequent algal pressure. 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. Within the 5 graded lakes of Watonwan County, Unnamed Lake sits at rank 4, near the bottom of the county list.

Unnamed Lake has no invasive species recorded in Minnesota state databases as of 2022, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Unnamed Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The lake lacks a documented public access point, so visitor use is limited. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.

Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2022-06-22. Grade methodology: LakeGrade methodology.

Swimming Safety

Avoid swimming, very poor water quality, potential algae toxins

Water Quality Grade: F, Very Poor

Very murky, less than 1 ft of visibility. Phosphorus level: 275 µg/L. Trophic State Index: 81.

MetricValueGrade
Water Clarity (Secchi Depth)1 ftF
Phosphorus275 µg/LF
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)81Hypereutrophic

Very high nutrients, dense algae, poor clarity

Location

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County Ranking

Ranked #4 of 5 lakes in Watonwan County

Nearby Lakes in Watonwan County

State Parks Near Unnamed Lake

Hypereutrophic Lakes in Minnesota

Data Sources

Water quality data from the EPA Water Quality Portal

Grading methodology based on Metropolitan Council standards

Most recent sample: 2022-06-22

Monitoring stations: 1