Big Horn County Lake Quality
Wyoming, 10 lakes, average grade D (Poor)
Only 10 lakes in Big Horn 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-wide average grade is D — water quality issues are persistent across most of the monitored basins. 3 lakes fall into the F bracket outright.
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. Meadowlark Lake (B) is the cleanest in the county.
Quick Answers for Big Horn County
Planning a trip? Check special fishing regulations for Meadowlark Lake — or check the official Wyoming fishing regulations.
All Lakes in Big Horn County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Meadowlark Lake | B | 11.7 ft | - |
| 2 | Renner Reservoir D | B | - | 20 µg/L |
| 3 | Wardell Reservoir -D | C | - | 50 µg/L |
| 4 | Bighorn Lake | C | - | 64.5 µg/L |
| 5 | Yellowtail Reservoir Tpd | D | - | 75 µg/L |
| 6 | Mayland Pond | D | - | 60 µg/L |
| 7 | Horseshoe Reservoir | F | 1.8 ft | 140 µg/L |
| 8 | Yellowtail Reservoir Rpd | F | - | 95 µg/L |
| 9 | Unnamed Reservoir | F | - | 90 µg/L |
Other Counties in Wyoming
See how Big Horn County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 34 states.
Where to stay near Big Horn County
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Source: EPA National Aquatic Resource Surveys, 2026.