Argenteuil County, Québec · Water Quality Report Card
Lac Sir-John
Lac Sir-John in Argenteuil, Québec received a water quality grade of A (Excellent). Water clarity: 4.1 m visibility. Phosphorus: 5.2 µg/L. Chlorophyll-a (algae): 2.7 µg/L.
- Clarity
- 4.1 m
- Type
- Oligotrophic
Lac Sir-John is a cold, clear oligotrophic lake in Argenteuil County, Québec. Water quality is graded A based on 3 sampling years through 2025. Compared to the 47 other monitored lakes in Argenteuil County, Lac Sir-John ranks #15 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
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Good clarity, visible to about 13.5 ft. Phosphorus level: 5.2 µg/L. Chlorophyll-a: 2.7 µg/L. Trophic State Index: 36.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 4.1 m | B |
| Phosphorus | 5.2 µg/L | A |
| Chlorophyll-a (Algae) | 2.7 µg/L | A |
| Trophic State Index (TSI) | 36 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Lac Sir-John
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Fishing Lac Sir-John
Location
County Ranking
Ranked #15 of 48 lakes in Argenteuil
Nearby Lakes in Argenteuil
Explore Lac Sir-John 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 Sir-John 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: