Sheridan County Lake Quality
Wyoming, 11 lakes, average grade B (Good)
Sheridan County has 11 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. 5 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. With an average grade of B, Sheridan County sits comfortably above the Wyoming median.
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. Sibley Lake (B) is the cleanest in the county.
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Quick Answers for Sheridan County
Planning a trip? Check special fishing regulations for Sibley Lake — or check the official Wyoming fishing regulations.
All Lakes in Sheridan County
11 lakes · 5 graded, 6 not rated5 graded lakes · 6 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | BSibley LakeSheridan | B | 9.2 ft | 10 µg/L | No recent samples | No recent samples | ✓ Public |
| 2 | BPark ReservoirSheridan | B | 10.8 ft | 10 µg/L | No recent samples | No recent samples | Not recorded |
| 3 | BMavrakis PondSheridan | B | 0.9 ft | 50 µg/L | No recent samples | No recent samples | Not recorded |
| 4 | BSawmill Reservoir DSheridan | B | No recent samples | 20 µg/L | No recent samples | No recent samples | Not recorded |
| 5 | BTwin Lakes Reservoir DSheridan | B | No recent samples | 10 µg/L | No recent samples | No recent samples | Not recorded |
| NRKleenburn PondSheridan | NR | 11.5 ft | 15 µg/L | No recent samples | No recent samples | Not recorded | |
| NRFivemile ReservoirSheridan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRWagner ReservoirSheridan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRDome Lake ReservoirSheridan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRDome LakeSheridan | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRWeston ReservoirSheridan | 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 Wyoming
See how Sheridan 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.