North Turtle Lake vs South Turtle Lake
Water quality, depth, fish species, and recreation comparison.
South Turtle Lake has a higher water quality grade (A, Excellent) than North Turtle Lake (D, Poor). Both are in Otter Tail County, Minnesota.
Both North Turtle Lake and South Turtle Lake sit in Minnesota. A same-state comparison strips out the state-level water-quality regime as a variable: any grade differences here are about the lakes themselves, not the agencies grading them. The grades are meaningfully apart: South Turtle Lake grades a A while North Turtle Lake grades a D. That two-letter spread reflects real underlying differences — different watershed inputs, different depth profiles, or different monitoring rigor.
For a recreational visitor, the wider grade gap is decisive — South Turtle Lake is the better water-quality choice. For a researcher, the gap is the interesting part: what is different about the two watersheds, and which of those differences is mutable?
North Turtle Lake
Murky, only visible to about 4 ft.
South Turtle Lake
Good clarity, visible to about 14.1 ft.
Side-by-Side Metrics
| Metric | North Turtle Lake | South Turtle Lake |
|---|---|---|
| Overall Grade | D (Poor) | A (Excellent) |
| Water Clarity | 4 ft | 14.1 ft |
| Phosphorus | 54.5 µg/L | 20 µg/L |
| Chlorophyll-a (Algae) | 22 µg/L | 3.7 µg/L |
| Maximum Depth | 19 ft | 35 ft |
| Surface Area | 1,773 acres | 837 acres |
| Public Access | Yes | Yes |
| Fish Species | 12 | 13 |
| Trophic State | eutrophic | mesotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
South Turtle Lake wins on overall water quality with a Grade A versus North Turtle Lake's Grade D. Water clarity: 14.1 ft vs 4 ft. For fishing diversity, South Turtle Lake also leads with 13 species.
Source: EPA National Aquatic Resource Surveys, 2026.