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F

Simon Lake

Pope County, MinnesotaHypereutrophic

Simon Lake grades an F: every scored parameter (clarity and phosphorus) rates poorly, placing it among the most stressed lakes monitored in Minnesota. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.

The hypereutrophic status — TSI 73 — 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 25 graded lakes of Pope County, Simon Lake sits at rank 25, near the bottom of the county list.

Simon Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Simon Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Simon Lake — most use is by shoreline residents and their guests. 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 2024-09-16. 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 1.3 ft of visibility. Phosphorus level: 117.5 µg/L. Trophic State Index: 73.

MetricValueGrade
Water Clarity (Secchi Depth)1.3 ftF
Phosphorus117.5 µg/LF
Chlorophyll-a (Algae)No data
Trophic State Index (TSI)73Hypereutrophic

Very high nutrients, dense algae, poor clarity

Water Quality Trend: Declining

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

MetricTrendChange/YearYears
Water Clarity Declining-0.06 m/yr5
Phosphorus Declining+4.65 µg/L/yr5
See year-by-year chart →

Location

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County Ranking

Ranked #25 of 25 lakes in Pope County

Cleaner Lakes Within 30 Miles

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

See full comparison →

Nearby Lakes in Pope County

Hypereutrophic Lakes in Minnesota

DNR Reports & Resources

Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Simon Lake. 2 reports on file.

EPA Impairment Status

Simon 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 MN61-0034-00 · 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: 2024-09-16

Monitoring stations: 1