Big Stone Lake
Big Stone County, MinnesotaEutrophic
Big Stone Lake pulls a D on the LakeGrade rubric — phosphorus loading and limited clarity hold it below the Minnesota average. The two scored sub-grades — clarity and phosphorus — track close together, so neither one is dragging the average down.
Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. 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. Big Stone Lake ranks 4 of 9 in Big Stone County — solidly in the upper half of the local distribution.
No invasive species are currently listed at Big Stone Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Big Stone Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2023-08-09. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Murky, only visible to about 3.9 ft. Phosphorus level: 217 µg/L. Trophic State Index: 70.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.9 ft | D |
| Phosphorus | 217 µg/L | F |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 70 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Location
County Ranking
Ranked #4 of 9 lakes in Big Stone County
Cleaner Lakes Within 30 Miles
Big Stone Lake holds Grade D. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Big Stone County
More Minnesota Lake Rankings
State Parks Near Big Stone Lake
Other Grade D Lakes in Minnesota
Eutrophic Lakes in Minnesota
EPA Impairment Status
Big Stone 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 MN06-0152-00 · 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: 2023-08-09
Monitoring stations: 4