Grand Isle County Lake Quality
Vermont, 3 lakes, average grade A (Excellent)
Grand Isle County has 3 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. The county's average grade is A — among the cleanest in {{stateName}}. 1 lakes pull an A on their own, and almost none fall into the D or F brackets.
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 Isle la Motte Lake (A); the most-stressed is Northeast Arm Lake (B).
Quick Answers for Grand Isle County
Planning a trip? Check special fishing regulations for Isle la Motte Lake — or check the official Vermont fishing regulations.
All Lakes in Grand Isle County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Isle la Motte Lake | A | 15.1 ft | 19.9 µg/L |
| 2 | Northeast Arm Lake | B | 13.3 ft | 19.6 µg/L |
| 3 | Northeast Arm Lake | B | 10.2 ft | 29.4 µg/L |
Other Counties in Vermont
See how Grand Isle County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 17 states.
Where to stay near Grand Isle County
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Source: EPA National Aquatic Resource Surveys, 2026.