Custer County Lake Quality
Idaho, 2 lakes, average grade B (Good)
Only 2 lakes in Custer 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. With an average grade of B, Custer County sits comfortably above the {{stateName}} 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. Nla Lake (A) is the cleanest in the county.
Quick Answers for Custer County
Planning a trip? Check special fishing regulations for Nla Lake — or check the official Idaho fishing regulations.
All Lakes in Custer County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Nla Lake | A | - | 17.7 µg/L |
| 2 | Nla Lake | B | 38.1 ft | 9000 µg/L |
Other Counties in Idaho
See how Custer 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 Custer County
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Source: EPA National Aquatic Resource Surveys, 2026.