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C

Hart Lake

Hubbard County, MinnesotaEutrophic

Hart Lake sits at a C on the grading scale — not impaired, not pristine, with summer measurements that vary year to year. clarity and phosphorus rate similarly, so there is no obvious single lever to pull on watershed management.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. A maximum depth of just 13 ft means sediment-bound phosphorus releases back into the water column whenever wind stirs the bottom — a classic shallow-lake dynamic. Hart Lake covers 226 acres alongside 2.6 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Hart Lake ranks 75 of 76 in Hubbard County — at the lower end of the locally monitored distribution.

Hart Lake has no invasive species recorded in Minnesota state databases as of 2023, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Hart Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Public access is available — the lake is on the Minnesota PCA public-access list. 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 2023-09-28. Grade methodology: LakeGrade methodology.

Reviewed by LakeQuality Editorial Team · Updated

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Swimming Safety

Generally safe for swimming, moderate water quality

Water Quality Grade: C, Fair

Murky, only visible to about 4.5 ft. Phosphorus level: 46 µg/L. Trophic State Index: 57.

MetricValueGrade
Water Clarity (Secchi Depth)4.5 ftD
Phosphorus46 µg/LC
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)57Eutrophic

High nutrients, frequent algae, reduced clarity

Lake Details

CharacteristicValue
Maximum Depth13 ft
Surface Area226.31 acres
Shoreline Length2.6 mi
Littoral Zone100%
Public AccessYes

Water Quality Trend: Declining

Based on 2 years of monitoring data (2020-2025).

MetricTrendChange/YearYears
Water Clarity Declining-0.067 m/yr2
Phosphorus Declining+3 µg/L/yr2

Location

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County Ranking

Ranked #75 of 76 lakes in Hubbard County

Cleaner Lakes Within 30 Miles

Hart Lake holds Grade C. 5 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Hubbard County

DNR Fisheries Survey Summary

1 survey on file from MN DNR Fisheries. Most recent: 1977-07-14 (Standard Survey).

Top Species by Catch Rate

SpeciesAvg CPUEAvg Weight
Black Bullhead79.130.66 lb
Yellow Perch9.380.51 lb
White Sucker1.631.6 lb
Northern Pike1.131.29 lb
Walleye1.001.9 lb
Pumpkinseed0.750.2 lb

CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.

From the 1977-07-14 survey

Mostly Bullheads. Bullheads and Yellow Perch higher than statewide average in the net catch. Northern Pike, Walleye and Panfish lower.

Source: MN DNR LakeFinder Fisheries Lake Survey

DNR Reports & Resources

Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Hart Lake. 3 reports on file.

EPA Impairment Status

Hart Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).

Causes of impairment

Nutrients (phosphorus, nitrogen)

Source: EPA ATTAINS assessment unit MN29-0063-00 · 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

Lake details from Minnesota DNR LakeFinder

Most recent sample: 2023-09-28

Monitoring stations: 1