Twin Falls County Lake Quality
Idaho, 1 lakes, average grade D (Poor)
Twin Falls County has 1 graded 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. On average, Twin Falls County lakes grade D, with phosphorus loading and reduced clarity showing up across most of the dataset.
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 (D) is the cleanest in the county.
Quick Answers for Twin Falls County
Planning a trip? Check special fishing regulations for Nla Lake — or check the official Idaho fishing regulations.
All Lakes in Twin Falls County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Nla Lake | D | 5.6 ft | 84000 µg/L |
Other Counties in Idaho
See how Twin Falls 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 Twin Falls County
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Source: EPA National Aquatic Resource Surveys, 2026.