Cassia County Lake Quality
Idaho, 3 lakes, average grade C (Fair)
Only 3 lakes in Cassia 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 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 Nla Lake (C); the most-stressed is Nla Lake (C).
Quick Answers for Cassia County
Planning a trip? Check special fishing regulations for Nla Lake — or check the official Idaho fishing regulations.
All Lakes in Cassia County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Nla Lake | C | 4.7 ft | 84.8 µg/L |
| 2 | Nla Lake | C | 3 ft | 1.9 µg/L |
| 3 | Lake Walcott | C | 4.3 ft | 50.5 µg/L |
Other Counties in Idaho
See how Cassia 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 Cassia County
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Source: EPA National Aquatic Resource Surveys, 2026.