Mahnomen County Lake Quality
Minnesota, 16 lakes, average grade C (Fair)
There are 16 graded lakes in Mahnomen County. The mix is varied enough that the county-level average tells you the broad strokes, not the choose-this-cabin specifics. The county average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Bass Lake (A); the most-stressed is Beaulieu Lake (F).
Quick Answers for Mahnomen County
Planning a trip? Check special fishing regulations for Bass Lake, whether the fish are safe to eat, and the best times to fish — or browse the full Minnesota regulations index.
DNR Reports (36)
Minnesota DNR LakeFinder resources for lakes in Mahnomen County. Showing 12 most recent — browse all reports →
- —Fisheries Lake Survey — TulabyFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — South TwinFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — SniderFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — SargentFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — RoyFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — North TwinFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — LoneFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — Little ElbowFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — IslandFisheries Lake Survey · MN DNR LakeFinder
- —Fisheries Lake Survey — BassFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Bass (0110)Aquatic Plant Report · MN DNR LakeFinder
- —Fish Stocking History — BassFish Stocking History · MN DNR LakeFinder
All Lakes in Mahnomen County
| Rank | Lake | Grade | Clarity | Max Depth | Phosphorus |
|---|---|---|---|---|---|
| 1 | Bass Lake | A | 13.1 ft | 26 ft | 10 µg/L |
| 2 | Mccraney Lake | A | 12.1 ft | - | 19 µg/L |
| 3 | South Twin Lake | A | 10.2 ft | 29 ft | 14 µg/L |
| 4 | Norris Lake | A | 11.6 ft | - | 15 µg/L |
| 5 | North Twin Lake | B | 8.5 ft | 16 ft | 17 µg/L |
| 6 | Sargent Lake | B | 8.9 ft | 15 ft | 16 µg/L |
| 7 | Tulaby Lake | B | 7.5 ft | 43 ft | 23.5 µg/L |
| 8 | Snider Lake | B | 8.5 ft | 29 ft | 21 µg/L |
| 9 | Little Elbow Lake | B | 6.9 ft | 18 ft | 21 µg/L |
| 10 | Roy Lake | C | 6 ft | 16 ft | 24 µg/L |
| 11 | Lone Lake | C | 7.1 ft | 22 ft | 48.5 µg/L |
| 12 | Unnamed Lake | C | 3.3 ft | - | 23 µg/L |
| 13 | Island Lake | C | 6.4 ft | 43 ft | 30 µg/L |
| 14 | Big Lake | D | 2.1 ft | - | 33 µg/L |
| 15 | Unnamed Lake | D | 3.3 ft | - | 60 µg/L |
| 16 | Beaulieu Lake | F | 1.3 ft | - | 90 µg/L |
Source: EPA National Aquatic Resource Surveys, 2026.