Mountrail County Lake Quality
North Dakota, 9 lakes, average grade C (Fair)
Mountrail County has 9 monitored lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. 4 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. The county average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.
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. Powers Lake (B) is the cleanest in the county.
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Quick Answers for Mountrail County
Planning a trip? Check special fishing regulations for Powers Lake — or check the official North Dakota fishing regulations.
All Lakes in Mountrail County
9 lakes · 4 graded, 5 not rated4 graded lakes · 5 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | BPowers LakeMountrail | B | 5.6 ft | 184 µg/L | 7.9 µg/L | No recent samples | ✓ Public |
| 2 | DStanley ReservoirMountrail | D | 1.1 ft | 395 µg/L | 19.5 µg/L | No recent samples | ✓ Public |
| 3 | DWhite Earth Dam LakeMountrail | D | 3 ft | 279.5 µg/L | 3.5 µg/L | No recent samples | ✓ Public |
| 4 | DClearwater LakeMountrail | D | 2.1 ft | 56 µg/L | 4.1 µg/L | No recent samples | ✓ Public |
| NRWhite LakeMountrail | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRKittelson SloughMountrail | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRLower Lostwood LakeMountrail | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRCottonwood LakeMountrail | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRShell LakeMountrail | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded |
NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
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Other Counties in North Dakota
See how Mountrail County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..
Source: EPA National Aquatic Resource Surveys, 2026.