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F

Wilhelm Lake

Wright County, MinnesotaHypereutrophic

Wilhelm Lake grades an F: every scored parameter (clarity and phosphorus) rates poorly, placing it among the most stressed lakes monitored in Minnesota. clarity and phosphorus rate similarly, so there is no obvious single lever to pull on watershed management.

Hypereutrophic conditions mean the lake is operating at the upper end of the productivity scale, with all the bloom risk that implies. 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 64 graded lakes of Wright County, Wilhelm Lake sits at rank 61, near the bottom of the county list.

No invasive species are currently listed at Wilhelm Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Wilhelm 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 2024-09-15. Grade methodology: LakeGrade methodology.

Reviewed by LakeQuality Editorial Team · Updated

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Swimming Safety

Avoid swimming, very poor water quality, potential algae toxins

Water Quality Grade: F, Very Poor

Very murky, less than 2 ft of visibility. Phosphorus level: 131 µg/L. Trophic State Index: 71.

MetricValueGrade
Water Clarity (Secchi Depth)2 ftF
Phosphorus131 µg/LF
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)71Hypereutrophic

Very high nutrients, dense algae, poor clarity

Water Quality Trend: Improving

Based on 5 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Improving+0.032 m/yr5
Phosphorus Improving-49.85 µg/L/yr5
See year-by-year chart →

Location

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County Ranking

Ranked #61 of 64 lakes in Wright County

Cleaner Lakes Within 30 Miles

Wilhelm Lake holds Grade F. 4 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Wright County

State Parks Near Wilhelm Lake

Hypereutrophic Lakes in Minnesota

EPA Impairment Status

Wilhelm Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).

Causes of impairment

Nutrients (phosphorus, nitrogen)

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit MN86-0020-00 · Official waterbody report

Data Sources

Water quality data from the EPA Water Quality Portal

Impairment status from EPA ATTAINS 303(d) database

Grading methodology based on Metropolitan Council standards

Most recent sample: 2024-09-15

Monitoring stations: 1