Is Petit Lac Saint-Mathieu safe to swim in?

Good for swimming, clear water with low algae levels. Petit Lac Saint-Mathieu has an overall water quality grade of B. Algae concentration (chlorophyll-a) is 3.2 µg/L. Always check local health department advisories before swimming.

Les Basques County, Québec · Water Quality Report Card

Petit Lac Saint-Mathieu

Grade B — Good

Mesotrophic

Petit Lac Saint-Mathieu in Les Basques, Québec received a water quality grade of B (Good). Water clarity: 1.6 m visibility. Phosphorus: 12.6 µg/L. Chlorophyll-a (algae): 3.2 µg/L.

Clarity: 1.6 m
Type: Mesotrophic

Where to stay →Safe to swim?

Petit Lac Saint-Mathieu is a mesotrophic lake in Les Basques County, Québec. Water quality is graded B based on 3 sampling years through 2025. Compared to the 1 other monitored lakes in Les Basques County, Petit Lac Saint-Mathieu ranks #2 for water quality.

Source: EPA Water Quality Portal sampling records, MELCCFP, last sampled 2025-08-01. Grade methodology: LakeGrade methodology.

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Swimming Safety

Good for swimming, clear water with low algae levels

Water Quality Grade: B, Good

Murky, only visible to about 5.2 ft. Phosphorus level: 12.6 µg/L. Chlorophyll-a: 3.2 µg/L. Trophic State Index: 45.

Metric	Value	Grade
Water Clarity (Secchi Depth)	1.6 m	D
Phosphorus	12.6 µg/L	A
Chlorophyll-a (Algae)	3.2 µg/L	A
Trophic State Index (TSI)	45	Mesotrophic

Moderate nutrients, good water quality

Where to stay near Petit Lac Saint-Mathieu

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