Haliburton County, Ontario · Water Quality Report Card
Big Barnum Lake
Big Barnum Lake in Haliburton, Ontario received a water quality grade of A (Excellent). Water clarity: 6 m visibility. Phosphorus: 5.3 µg/L.
- Clarity
- 6 m
- Type
- Oligotrophic
Big Barnum Lake is a cold, clear oligotrophic lake in Haliburton County, Ontario. Water quality is graded A based on 2 sampling years through 2025. Compared to the 217 other monitored lakes in Haliburton County, Big Barnum Lake ranks #5 for water quality.
Source: EPA Water Quality Portal sampling records, Ontario MECP, last sampled 2025-10-01. Grade methodology: LakeGrade methodology.
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Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 19.7 ft down. Phosphorus level: 5.3 µg/L. Trophic State Index: 31.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6 m | A |
| Phosphorus | 5.3 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 31 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
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Fishing Big Barnum Lake
Location
County Ranking
Ranked #5 of 218 lakes in Haliburton
Nearby Lakes in Haliburton
Explore Big Barnum Lake across LakeGrade
More Ontario Lake Rankings
Other Grade A Lakes in Ontario
Oligotrophic Lakes in Ontario
More records, surveys & data sources
Where this data comes from
Measurements for Big Barnum 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: 2025-10-01
Monitoring stations: