Manitoulin District County, Ontario · Water Quality Report Card
Big Lake
Big Lake in Manitoulin District, Ontario received a water quality grade of B (Good). Water clarity: 2.8 m visibility. Phosphorus: 7.5 µg/L.
- Clarity
- 2.8 m
- Type
- Oligotrophic
Big Lake is a cold, clear oligotrophic lake in Manitoulin District County, Ontario. Water quality is graded B based on 2 sampling years through 2025. Compared to the 12 other monitored lakes in Manitoulin District County, Big Lake ranks #10 for water quality.
Source: EPA Water Quality Portal sampling records, Ontario MECP, last sampled 2025-10-26. 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 9.2 ft. Phosphorus level: 7.5 µg/L. Trophic State Index: 39.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.8 m | C |
| Phosphorus | 7.5 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 39 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
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Fishing Big Lake
Location
County Ranking
Ranked #10 of 13 lakes in Manitoulin District
Cleaner Lakes Within 30 Miles
Big Lake holds Grade B. 5 nearby lakes hold higher grades.
- AManitou LakeManitoulin District · 5.3 mi · Higher grade (B → A)
- AKagawong LakeManitoulin District · 11.5 mi · Higher grade (B → A)
- AKagawong LakeManitoulin District · 12.1 mi · Higher grade (B → A)
- ANameless LakeManitoulin District · 18.2 mi · Higher grade (B → A)
- AWindfall LakeManitoulin District · 2.5 mi · Higher grade (B → A)
Nearby Lakes in Manitoulin District
Explore Big Lake across LakeGrade
More Ontario Lake Rankings
Other Grade B Lakes in Ontario
Oligotrophic Lakes in Ontario
More records, surveys & data sources
Where this data comes from
Measurements for Big Lake 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: 2025-10-26
Monitoring stations: