Urban agglomeration of Longueuil County, Québec · Water Quality Report Card
Lac Seigneurial
Lac Seigneurial in Urban agglomeration of Longueuil, Québec received a water quality grade of B (Good). Water clarity: 3.6 m visibility. Phosphorus: 14.5 µg/L. Chlorophyll-a (algae): 6.7 µg/L.
- Clarity
- 3.6 m
- Type
- Mesotrophic
Lac Seigneurial is a mesotrophic lake in Urban agglomeration of Longueuil County, Québec. Water quality is graded B based on 3 sampling years through 2025. Compared to the 4 other monitored lakes in Urban agglomeration of Longueuil County, Lac Seigneurial ranks #3 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
Good clarity, visible to about 11.8 ft. Phosphorus level: 14.5 µg/L. Chlorophyll-a: 6.7 µg/L. Trophic State Index: 45.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.6 m | B |
| Phosphorus | 14.5 µg/L | A |
| Chlorophyll-a (Algae) | 6.7 µg/L | B |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Lac Seigneurial
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Fishing Lac Seigneurial
Location
County Ranking
Ranked #3 of 5 lakes in Urban agglomeration of Longueuil
Cleaner Lakes Within 30 Miles
Lac Seigneurial holds Grade B. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Urban agglomeration of Longueuil
Explore Lac Seigneurial across LakeGrade
More Québec Lake Rankings
Other Grade B Lakes in Québec
Mesotrophic Lakes in Québec
More records, surveys & data sources
Where this data comes from
Measurements for Lac Seigneurial 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: