Black Brook Flowage Lake vs South Twin Lake
Water quality, depth, fish species, and recreation comparison.
South Twin Lake has a higher water quality grade (A, Excellent) than Black Brook Flowage Lake (B, Good). Both are in Polk County, Wisconsin.
Black Brook Flowage Lake and South Twin Lake are both in Wisconsin — 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: Black Brook Flowage Lake (B) and South Twin 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.
Black Brook Flowage Lake
Good clarity, visible to about 10.5 ft.
South Twin Lake
No clarity data.
Side-by-Side Metrics
| Metric | Black Brook Flowage Lake | South Twin Lake |
|---|---|---|
| Overall Grade | B (Good) | A (Excellent) |
| Water Clarity | 10.5 ft | No data |
| Phosphorus | 46.6 µg/L | 11.7 µg/L |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | - | - |
| Surface Area | 98 acres | 639 acres |
| Public Access | Unknown | Unknown |
| Fish Species | 0 | 0 |
| Trophic State | eutrophic | oligotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
South Twin Lake wins on overall water quality with a Grade A versus Black Brook Flowage Lake's Grade B. For fishing diversity, South Twin Lake also leads with 0 species.