Les Pays-d'en-Haut County, Québec · Water Quality Report Card
Lac Saint-Louis
Lac Saint-Louis in Les Pays-d'en-Haut, Québec received a water quality grade of A (Excellent). Water clarity: 5.3 m visibility. Phosphorus: 4.8 µg/L. Chlorophyll-a (algae): 1.7 µg/L.
- Clarity
- 5.3 m
- Type
- Oligotrophic
Lac Saint-Louis is a cold, clear oligotrophic lake in Les Pays-d'en-Haut County, Québec. Water quality is graded A based on 3 sampling years through 2025. Compared to the 108 other monitored lakes in Les Pays-d'en-Haut County, Lac Saint-Louis ranks #19 for water quality.
Source: EPA Water Quality Portal sampling records, MELCCFP, last sampled 2025-08-01. Grade methodology: LakeGrade methodology.
Watch Lac Saint-Louis water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 17.2 ft down. Phosphorus level: 4.8 µg/L. Chlorophyll-a: 1.7 µg/L. Trophic State Index: 33.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.25 m | A |
| Phosphorus | 4.8 µg/L | A |
| Chlorophyll-a (Algae) | 1.7 µg/L | A |
| Trophic State Index (TSI) | 33 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Lac Saint-Louis
Compare lakeside cabins, hotels, and vacation rentals near Lac Saint-Louis in Les Pays-d'en-Haut, Québec — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Lac Saint-Louis
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to Lac Saint-Louis?
Get lake water-quality report cards plus the best cabin & lodging deals near Lac Saint-Louis — straight to your inbox. No spam, unsubscribe anytime.
Fishing Lac Saint-Louis
Location
County Ranking
Ranked #19 of 109 lakes in Les Pays-d'en-Haut
Nearby Lakes in Les Pays-d'en-Haut
Explore Lac Saint-Louis across LakeGrade
More Québec Lake Rankings
Other Grade A Lakes in Québec
Oligotrophic Lakes in Québec
More records, surveys & data sources
Where this data comes from
Measurements for Lac Saint-Louis come from the EPA Water Quality Portal. Per-sample source details are not recorded for this lake.
Data Sources
Water quality data from the EPA Water Quality Portal
Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion
Most recent sample: 2025-08-01
Monitoring stations: