Valley County Lake Quality
Montana, 5 lakes, average grade C (Fair)
Valley County has 5 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. Valley County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.
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 (B) is the cleanest in the county.
Quick Answers for Valley County
Planning a trip? Check special fishing regulations for Nla Lake — or check the official Montana fishing regulations.
All Lakes in Valley County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Nla Lake | B | 7.1 ft | 26.3 µg/L |
| 2 | Nla Lake | D | 2.1 ft | 46000 µg/L |
| 3 | Nla Lake | F | 1 ft | 336.5 µg/L |
Other Counties in Montana
See how Valley 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 Valley County
Top-rated places to stay near Valley County
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to Valley County?
Get lake water-quality report cards plus the best cabin & lodging deals near Valley County — straight to your inbox. No spam, unsubscribe anytime.
Source: EPA National Aquatic Resource Surveys, 2026.