Three Island Lake vs Turtle Lake
Water quality, depth, fish species, and recreation comparison.
Three Island Lake and Turtle Lake both received the same overall water quality grade of A (Excellent). Both are in Beltrami County, Minnesota.
Three Island Lake and Turtle Lake are both in Minnesota — a same-state head-to-head where the comparison comes down to lake-specific differences in depth, watershed, and monitoring history rather than the broader state-level water-quality regime. The grades are close: Three Island Lake (A) and Turtle Lake (A) are within one letter of each other on the LakeGrade rubric. The per-parameter sub-grades below will show where the small differences actually live.
With grades this close, the choice between the two lakes turns on non-water-quality factors: depth, fish species, public access, distance from home. The per-lake pages below cover all of those.
Three Island Lake
Good clarity, visible to about 11.8 ft.
Turtle Lake
Good clarity, visible to about 10.2 ft.
Side-by-Side Metrics
| Metric | Three Island Lake | Turtle Lake |
|---|---|---|
| Overall Grade | A (Excellent) | A (Excellent) |
| Water Clarity | 11.8 ft | 10.2 ft |
| Phosphorus | 17 µg/L | 15 µg/L |
| Chlorophyll-a (Algae) | 4.1 µg/L | 4.9 µg/L |
| Maximum Depth | 25 ft | 45 ft |
| Surface Area | 729 acres | 1,607 acres |
| Public Access | Yes | Yes |
| Fish Species | 17 | 16 |
| Trophic State | mesotrophic | mesotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Both lakes earn the same Grade A. The tiebreakers come down to clarity (Three Island Lake: 11.8 ft, Turtle Lake: 10.2 ft) and what you want from the lake. Three Island Lake supports more documented fish species.
Source: EPA National Aquatic Resource Surveys, 2026.