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F

Mud Lake

Hennepin County, MinnesotaHypereutrophic

On the LakeGrade rubric Mud Lake fails the cutoffs — a TSI of 77 and persistent algal pressure put it in the bottom tier. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.

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 Hennepin County's 95 graded lakes, Mud Lake ranks 59 — below the local median, though not at the bottom.

Eurasian watermilfoil has been documented at Mud Lake, requiring shoreline management to keep dense mats from crowding native vegetation. The state fisheries records do not list documented species for Mud 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 2021-09-13. 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 0.9 ft of visibility. Phosphorus level: 150 µg/L. Trophic State Index: 77.

MetricValueGrade
Water Clarity (Secchi Depth)0.9 ftF
Phosphorus150 µg/LF
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)77Hypereutrophic

Very high nutrients, dense algae, poor clarity

Invasive & Introduced Species

Red chips are ecologically harmful invasive species. Gray chips are stocked or introduced fish that aren't a current ecological concern.

Eurasian watermilfoil

Water Quality Trend: Improving

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

MetricTrendChange/YearYears
Water Clarity Improving+0.065 m/yr5
Phosphorus Improving-2.45 µg/L/yr5
See year-by-year chart →

Location

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County Ranking

Ranked #59 of 95 lakes in Hennepin County

Cleaner Lakes Within 30 Miles

Mud Lake holds Grade F. 5 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Hennepin County

Hypereutrophic Lakes in Minnesota

EPA Impairment Status

Mud 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 MN10-0042-00 · Official waterbody report · Matched by proximity (1.47 km)

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: 2021-09-13

Monitoring stations: 1