Big Lake vs Little Turtle Lake
Water quality, depth, fish species, and recreation comparison.
Big Lake has a higher water quality grade (A, Excellent) than Little Turtle Lake (C, Fair). Both are in Beltrami County, Minnesota.
Both Big Lake and Little 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. Big Lake (A) is materially cleaner than Little Turtle Lake (C). A gap that wide is unlikely to close in a single year of remediation work; it reflects multi-decade differences in the lakes themselves.
For a recreational visitor, the wider grade gap is decisive — Big 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?
Big Lake
Moderate clarity, visible to about 9.7 ft.
Little Turtle Lake
Murky, only visible to about 6.5 ft.
Side-by-Side Metrics
| Metric | Big Lake | Little Turtle Lake |
|---|---|---|
| Overall Grade | A (Excellent) | C (Fair) |
| Water Clarity | 9.7 ft | 6.5 ft |
| Phosphorus | 15 µg/L | 23.5 µg/L |
| Chlorophyll-a (Algae) | 4.8 µg/L | 12 µg/L |
| Maximum Depth | 35 ft | 25 ft |
| Surface Area | 3,598 acres | 469 acres |
| Public Access | Yes | No |
| Fish Species | 17 | 15 |
| Trophic State | mesotrophic | eutrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Big Lake wins on overall water quality with a Grade A versus Little Turtle Lake's Grade C. Water clarity: 9.7 ft vs 6.5 ft. For fishing diversity, Big Lake also leads with 17 species.
Source: EPA National Aquatic Resource Surveys, 2026.