Les Collines-de-l'Outaouais County, Québec · Water Quality Report Card
Lac Johnston
Lac Johnston in Les Collines-de-l'Outaouais, Québec received a water quality grade of A (Excellent). Water clarity: 3.7 m visibility. Phosphorus: 9.7 µg/L. Chlorophyll-a (algae): 3.1 µg/L.
- Clarity
- 3.7 m
- Type
- Oligotrophic
Lac Johnston is a cold, clear oligotrophic lake in Les Collines-de-l'Outaouais County, Québec. Water quality is graded A based on 3 sampling years through 2025. Compared to the 10 other monitored lakes in Les Collines-de-l'Outaouais County, Lac Johnston 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
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Good clarity, visible to about 12.1 ft. Phosphorus level: 9.7 µg/L. Chlorophyll-a: 3.1 µg/L. Trophic State Index: 40.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 3.7 m | B |
| Phosphorus | 9.7 µg/L | A |
| Chlorophyll-a (Algae) | 3.1 µg/L | A |
| Trophic State Index (TSI) | 40 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
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Fishing Lac Johnston
Location
County Ranking
Ranked #6 of 11 lakes in Les Collines-de-l'Outaouais
Nearby Lakes in Les Collines-de-l'Outaouais
Explore Lac Johnston across LakeGrade
More Québec Lake Rankings
Other Grade A Lakes in Québec
Oligotrophic Lakes in Québec
More records, surveys & data sources
Where this data comes from
Measurements for Lac Johnston 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: