Hill County Lake Quality
Montana, 2 lakes, average grade D (Poor)
Only 2 lakes in Hill 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, Hill 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 Hill County
Planning a trip? Check special fishing regulations for Nla Lake — or check the official Montana fishing regulations.
All Lakes in Hill County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Nla Lake | D | 4.2 ft | 339000 µg/L |
| 2 | Nla Lake | F | 0.8 ft | 390000 µg/L |
Other Counties in Montana
See how Hill 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 Hill County
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Source: EPA National Aquatic Resource Surveys, 2026.