Broadwater County Lake Quality
Montana, 3 lakes, average grade C (Fair)
Only 3 lakes in Broadwater 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 Island Park Reservoir (B); the most-stressed is Canyon Ferry Lake (C).
Quick Answers for Broadwater County
Planning a trip? Check special fishing regulations for Island Park Reservoir — or check the official Montana fishing regulations.
All Lakes in Broadwater County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Island Park Reservoir | B | - | 23.5 µg/L |
| 2 | Canyon Ferry Lake | C | 8.9 ft | 34 µg/L |
| 3 | Canyon Ferry Lake | C | 4.3 ft | 27 µg/L |
Other Counties in Montana
See how Broadwater 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 Broadwater County
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Source: EPA National Aquatic Resource Surveys, 2026.