Lac-Saint-Jean-Est County, Québec · Water Quality Report Card
Grand Lac Sec
Grand Lac Sec in Lac-Saint-Jean-Est, Québec received a water quality grade of B (Good). Water clarity: 2.7 m visibility. Phosphorus: 13 µg/L. Chlorophyll-a (algae): 3.8 µg/L.
- Clarity
- 2.7 m
- Type
- Mesotrophic
Grand Lac Sec is a mesotrophic lake in Lac-Saint-Jean-Est County, Québec. Water quality is graded B based on 3 sampling years through 2025. Compared to the 15 other monitored lakes in Lac-Saint-Jean-Est County, Grand Lac Sec ranks #12 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
Moderate clarity, visible to about 8.7 ft. Phosphorus level: 13 µg/L. Chlorophyll-a: 3.8 µg/L. Trophic State Index: 44.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.65 m | C |
| Phosphorus | 13 µg/L | A |
| Chlorophyll-a (Algae) | 3.8 µg/L | A |
| Trophic State Index (TSI) | 44 | Mesotrophic |
Moderate nutrients, good water quality
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Fishing Grand Lac Sec
Location
County Ranking
Ranked #12 of 16 lakes in Lac-Saint-Jean-Est
Cleaner Lakes Within 30 Miles
Grand Lac Sec holds Grade B. 4 nearby lakes hold higher grades.
- ALac de L'Aqueduc de Saint-BrunoLac-Saint-Jean-Est · 8 mi · Higher grade (B → A)
- ALac VertLac-Saint-Jean-Est · 4.4 mi · Higher grade (B → A)
- ALac à la CarpeLac-Saint-Jean-Est · 12.8 mi · Higher grade (B → A)
- ALac à AlmasLe Domaine-du-Roy · 13.8 mi · Higher grade (B → A)
Nearby Lakes in Lac-Saint-Jean-Est
Explore Grand Lac Sec 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 Grand Lac Sec 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: