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LakeQuality
B

Montmagny County Lake Quality

Québec, 2 lakes, average grade B (Good)

Only 2 lakes in Montmagny 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-wide average lands at B — solid water quality with most lakes carrying clear summer transparency and low-to-moderate phosphorus.

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 Lac Jally (B); the most-stressed is Lac FrontièRe (B).

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All Lakes in Montmagny County

RankLakeGradeClarityPhosphorus
1Lac JallyB8.9 ft8.5 µg/L
2Lac FrontièReB5.2 ft17.4 µg/L

See how Montmagny County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 38 states.

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Source: EPA National Aquatic Resource Surveys, 2026.