Montcalm County, Québec · Water Quality Report Card
Lac Duffy
Lac Duffy in Montcalm, Québec received a water quality grade of B (Good). Water clarity: 2.8 m visibility. Phosphorus: 9.9 µg/L. Chlorophyll-a (algae): 3.8 µg/L.
- Clarity
- 2.8 m
- Type
- Mesotrophic
Lac Duffy is a mesotrophic lake in Montcalm County, Québec. Water quality is graded B based on 3 sampling years through 2025. Compared to the 7 other monitored lakes in Montcalm County, Lac Duffy ranks #6 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 9 ft. Phosphorus level: 9.9 µg/L. Chlorophyll-a: 3.8 µg/L. Trophic State Index: 42.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.75 m | C |
| Phosphorus | 9.9 µg/L | A |
| Chlorophyll-a (Algae) | 3.8 µg/L | A |
| Trophic State Index (TSI) | 42 | Mesotrophic |
Moderate nutrients, good water quality
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Fishing Lac Duffy
Location
County Ranking
Ranked #6 of 8 lakes in Montcalm
Cleaner Lakes Within 30 Miles
Lac Duffy holds Grade B. 4 nearby lakes hold higher grades.
- ALac BeaulacMatawinie · 1.6 mi · Higher grade (B → A)
- ALac CristalMontcalm · 2.6 mi · Higher grade (B → A)
- ALac AshtonLes Pays-d'en-Haut · 4.7 mi · Higher grade (B → A)
- ALac MooneyMatawinie · 4.7 mi · Higher grade (B → A)
Nearby Lakes in Montcalm
Explore Lac Duffy 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 Duffy 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: