L'Érable County, Québec · Water Quality Report Card
Lac William
Lac William in L'Érable, Québec received a water quality grade of C (Fair). Water clarity: 1.9 m visibility. Phosphorus: 17.9 µg/L. Chlorophyll-a (algae): 10.6 µg/L.
- Clarity
- 1.9 m
- Type
- Eutrophic
Lac William is a productive, nutrient-rich eutrophic lake in L'Érable County, Québec. Water quality is graded C based on 3 sampling years through 2025. Compared to the 1 other monitored lakes in L'Érable County, Lac William ranks #2 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
Generally safe for swimming, moderate water quality
Water Quality Grade: C, Fair
Murky, only visible to about 6.2 ft. Phosphorus level: 17.9 µg/L. Chlorophyll-a: 10.6 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.9 m | D |
| Phosphorus | 17.9 µg/L | A |
| Chlorophyll-a (Algae) | 10.6 µg/L | C |
| Trophic State Index (TSI) | 50 | Eutrophic |
High nutrients, frequent algae, reduced clarity
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Fishing Lac William
Location
County Ranking
Ranked #2 of 2 lakes in L'Érable
Cleaner Lakes Within 30 Miles
Lac William holds Grade C. 4 nearby lakes hold higher grades.
- ALac BreechesLes Appalaches · 15.9 mi · Two grade letters higher (C → A)
- BLac de L'EstLes Appalaches · 14.5 mi · Higher grade (C → B)
- BPetit Lac Saint-FrançOisLes Appalaches · 17.3 mi · Higher grade (C → B)
- BLac CaribouLes Appalaches · 14 mi · Higher grade (C → B)
Nearby Lakes in L'Érable
Explore Lac William across LakeGrade
More Québec Lake Rankings
Other Grade C Lakes in Québec
Eutrophic Lakes in Québec
More records, surveys & data sources
Where this data comes from
Measurements for Lac William 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: