Muskoka District County, Ontario · 45.18°N · Water Quality Report Card
Three Mile Lake
Three Mile Lake in Muskoka District, Ontario received a water quality grade of C (Fair). Water clarity: 1.6 m visibility. Phosphorus: 21.8 µg/L.
- Clarity
- 1.6 m
- Type
- Eutrophic
Three Mile Lake is a productive, nutrient-rich eutrophic lake in Muskoka District County, Ontario. Water quality is graded C based on 2 sampling years through 2025. Compared to the 169 other monitored lakes in Muskoka District County, Three Mile Lake ranks #166 for water quality.
Source: EPA Water Quality Portal sampling records, Ontario MECP, last sampled 2025-10-16. Grade methodology: LakeGrade methodology.
Watch Three Mile Lake water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Generally safe for swimming, moderate water quality
Water Quality Grade: C, Fair
Murky, only visible to about 5.2 ft. Phosphorus level: 21.8 µg/L. Trophic State Index: 51.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 m | D |
| Phosphorus | 21.8 µg/L | B |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 51 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Three Mile Lake
Compare lakeside cabins, hotels, and vacation rentals near Three Mile Lake in Muskoka District, Ontario — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Three Mile Lake
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to Three Mile Lake?
Get lake water-quality report cards plus the best cabin & lodging deals near Three Mile Lake — straight to your inbox. No spam, unsubscribe anytime.
Fishing Three Mile Lake
Location
County Ranking
Ranked #166 of 170 lakes in Muskoka District
Cleaner Lakes Within 30 Miles
Three Mile Lake holds Grade C. 5 nearby lakes hold higher grades.
- ASkeleton LakeMuskoka District · 5.3 mi · Two grade letters higher (C → A)
- ANutt LakeMuskoka District · 2.5 mi · Two grade letters higher (C → A)
- AHigh LakeMuskoka District · 4.3 mi · Two grade letters higher (C → A)
- ALittle Long LakeMuskoka District · 5 mi · Two grade letters higher (C → A)
- BYoung LakeMuskoka District · 4.4 mi · Higher grade (C → B)
Nearby Lakes in Muskoka District
Explore Three Mile Lake across LakeGrade
More Ontario Lake Rankings
Other Grade C Lakes in Ontario
Eutrophic Lakes in Ontario
More records, surveys & data sources
Where this data comes from
Measurements for Three Mile 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: 2025-10-16
Monitoring stations: