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LakeQuality
C

Pontiac County Lake Quality

Ontario, 4 lakes, average grade C (Fair)

Only 4 lakes in Pontiac 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. Pontiac 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.

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 des Chats Lake (B); the most-stressed is Lac Coulonge Lake (D).

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All Lakes in Pontiac County

RankLakeGradeClarityPhosphorus
1Lac des Chats LakeB6.2 ft16.4 µg/L
2Lac du Rocher-Fendu LakeB5.2 ft13 µg/L
3Lower Allumette LakeB4.8 ft16.2 µg/L
4Lac Coulonge LakeD5.2 ft-

See how Pontiac 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.