School Grove Lake
Lyon County, MinnesotaLimited DataEutrophic
On the LakeGrade rubric School Grove Lake fails the cutoffs — a TSI of 67 and persistent algal pressure put it in the bottom tier.
Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. At only 11 ft deep, School Grove Lake is shallow — wind keeps the water column mixed and sediment resuspension drives phosphorus levels harder to manage. At 349 acres, School Grove Lake fits the Minnesota median for monitored lakes, with 5.0 miles of shoreline. Within the 5 graded lakes of Lyon County, School Grove Lake sits at rank 4, near the bottom of the county list.
No invasive species are currently listed at School Grove Lake — the lake remains off the Minnesota infested-waters roster. Walleye are documented at School Grove Lake, one of 10 fish species on record for the 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 2024-09-01. Grade methodology: LakeGrade methodology.
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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. Trophic State Index: 67.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2 ft | F |
| Phosphorus | No data | |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 67 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 11 ft |
| Surface Area | 348.67 acres |
| Shoreline Length | 5 mi |
| Littoral Zone | 100% |
| Public Access | Yes |
Fish Species
Click a species to see all Minnesota and Wisconsin lakes where it is found.
→ Best fishing times for School Grove Lake (14-day solunar calendar)
→ Is it safe to eat fish from School Grove Lake? (mercury & PFAS guide)
→ School Grove Lake fishing regulations (limits, seasons, special rules)
Water Quality Trend: ↓ Declining
Based on 3 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.035 m/yr | 3 |
Location
County Ranking
Ranked #4 of 5 lakes in Lyon County
Nearby Lakes in Lyon County
More Minnesota Lake Rankings
State Parks Near School Grove Lake
Other Grade F Lakes in Minnesota
Eutrophic Lakes in Minnesota
DNR Fisheries Survey Summary
16 surveys on file from MN DNR Fisheries. Most recent: 2025-09-08 (Targeted Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Black Bullhead | 156.15 | 0.2 lb |
| Walleye | 45.63 | 1.55 lb |
| Fathead Minnow | 29.70 | — |
| Black Crappie | 11.96 | 0.38 lb |
| Bluegill | 10.92 | 0.31 lb |
| Common Carp | 8.63 | 2.64 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
Length Distributions
Number of fish caught at each inch class in the most recent survey that recorded lengths. Red dashed line marks an approximate trophy threshold for that species.
Black Bullhead
Walleye
Black Crappie
Bluegill
From the 2025-09-08 survey
A targeted fall night electrofishing survey was conducted on School Grove during September 8, 2025 to evaluate young of year "YOY" (fingerling sized) Walleye numbers due to a fry stocking. Three stations were sampled for a total of 30 minutes at night. Water temperature was 74.8 F. Water clarity was 6 inches. We saw…
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for School Grove Lake. 3 reports on file.
- —Fisheries Lake Survey — School GroveFisheries Lake Survey · MN DNR LakeFinder
- —Fish Stocking History — School GroveFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — School GrovePublic Water Access Sites · MN DNR LakeFinder
EPA Impairment Status
School Grove Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit MN42-0002-00 · 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: 2024-09-01
Monitoring stations: 1