Big Stone County Lake Quality
Minnesota, 9 lakes, average grade F (Very Poor)
Only 9 lakes in Big Stone County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. The county average is F — the most-stressed bracket in our rubric. Most monitored lakes here show persistent nutrient loading and algal pressure.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Unnamed Lake (D) is the cleanest in the county.
Quick Answers for Big Stone County
Planning a trip? Check special fishing regulations for Unnamed Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Minnesota regulations index.
DNR Reports (9)
Minnesota DNR LakeFinder resources for lakes in Big Stone County. browse all reports →
- —Fisheries Lake Survey — Long TomFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — OtreyFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — East ToquaFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — BarryFisheries Lake Survey · MN DNR LakeFinder
- —Public Water Access Sites — BarryPublic Water Access Sites · MN DNR LakeFinder
- —Fish Stocking History — East ToquaFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — East ToquaPublic Water Access Sites · MN DNR LakeFinder
- —Fish Stocking History — Long TomFish Stocking History · MN DNR LakeFinder
- —Public Water Access Sites — Long TomPublic Water Access Sites · MN DNR LakeFinder
All Lakes in Big Stone County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Unnamed Lake | D | 6.9 ft | - | 167.5 µg/L |
| 2 | Cup Lake | D | 5.1 ft | - | - |
| 3 | 06-0422-00 Lake | D | 2.6 ft | - | 43 µg/L |
| 4 | Big Stone Lake | D | 3.9 ft | - | 217 µg/L |
| 5 | Unnamed Lake | F | 2 ft | 15 ft | 518.5 µg/L |
| 6 | East Toqua Lake | F | 1.6 ft | 9 ft | 720 µg/L |
| 7 | Otrey Lake | F | 1 ft | 8 ft | 431 µg/L |
| 8 | Barry Lake | F | 0.8 ft | 8.8 ft | 348 µg/L |
| 9 | Olson Lake | F | 0.7 ft | - | 782 µg/L |
Source: EPA National Aquatic Resource Surveys, 2026.