Thunder Bay District County, Ontario · Water Quality Report Card
Jolly L. Lake
Jolly L. Lake in Thunder Bay District, Ontario received a water quality grade of B (Good). Water clarity: 1.6 m visibility. Phosphorus: 13.5 µg/L.
- Clarity
- 1.6 m
- Type
- Mesotrophic
Jolly L. Lake is a mesotrophic lake in Thunder Bay District County, Ontario. Water quality is graded B based on 2 sampling years through 2025. Compared to the 301 other monitored lakes in Thunder Bay District County, Jolly L. Lake ranks #241 for water quality.
Source: EPA Water Quality Portal sampling records, Ontario MECP, 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
Murky, only visible to about 5.2 ft. Phosphorus level: 13.5 µg/L. Trophic State Index: 47.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 m | D |
| Phosphorus | 13.5 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 47 | Mesotrophic |
Moderate nutrients, good water quality
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Fishing Jolly L. Lake
Location
County Ranking
Ranked #241 of 302 lakes in Thunder Bay District
Cleaner Lakes Within 30 Miles
Jolly L. Lake holds Grade B. 5 nearby lakes hold higher grades.
- AWalotka L. LakeThunder Bay District · 19.3 mi · Higher grade (B → A)
- AArnott LakeThunder Bay District · 23.3 mi · Higher grade (B → A)
- ADisraeli LakeThunder Bay District · 21.6 mi · Higher grade (B → A)
- BGennis LakeThunder Bay District · 16.3 mi · Higher overall water quality score
- BHine LakeThunder Bay District · 22.5 mi · Higher overall water quality score
Nearby Lakes in Thunder Bay District
Explore Jolly L. Lake across LakeGrade
More Ontario Lake Rankings
Other Grade B Lakes in Ontario
Mesotrophic Lakes in Ontario
More records, surveys & data sources
Where this data comes from
Measurements for Jolly L. 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: 2025-08-01
Monitoring stations: