Sheridan County Lake Quality
Montana, 3 lakes, average grade D (Poor)
Only 3 lakes in Sheridan 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. On average, Sheridan County lakes grade D, with phosphorus loading and reduced clarity showing up across most of the dataset.
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 Nla Lake (C); the most-stressed is Nla Lake (F).
Quick Answers for Sheridan County
Planning a trip? Check special fishing regulations for Nla Lake — or check the official Montana fishing regulations.
All Lakes in Sheridan County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Nla Lake | C | - | 355000 µg/L |
| 2 | Nla Lake | D | 1.9 ft | 108.7 µg/L |
| 3 | Nla Lake | F | 0.6 ft | 3436000 µg/L |
Other Counties in Montana
See how Sheridan 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 Sheridan County
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Source: EPA National Aquatic Resource Surveys, 2026.