Birch Lake vs Town Line Lake
Water quality, depth, fish species, and recreation comparison.
Birch Lake has a higher water quality grade (A, Excellent) than Town Line Lake (C, Fair). Both are in Cass County, Minnesota.
Both Birch Lake and Town Line 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. Birch Lake (A) is materially cleaner than Town Line 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 — Birch 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?
Birch Lake
Good clarity, visible to about 14 ft.
Town Line Lake
Murky, only visible to about 6.6 ft.
Side-by-Side Metrics
| Metric | Birch Lake | Town Line Lake |
|---|---|---|
| Overall Grade | A (Excellent) | C (Fair) |
| Water Clarity | 14 ft | 6.6 ft |
| Phosphorus | 12 µg/L | 11 µg/L |
| Chlorophyll-a (Algae) | 4 µg/L | 2.1 µg/L |
| Maximum Depth | 45 ft | 11 ft |
| Surface Area | 1,267 acres | 698 acres |
| Public Access | Yes | Yes |
| Fish Species | 14 | 8 |
| Trophic State | mesotrophic | mesotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Birch Lake wins on overall water quality with a Grade A versus Town Line Lake's Grade C. Water clarity: 14 ft vs 6.6 ft. For fishing diversity, Birch Lake also leads with 14 species.
Source: EPA National Aquatic Resource Surveys, 2026.