Lake Koshkonong vs Rock River Lake
Water quality, depth, fish species, and recreation comparison.
Rock River Lake has a higher water quality grade (A, Excellent) than Lake Koshkonong (F, Very Poor). Both are in Wisconsin.
Lake Koshkonong and Rock River 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. Rock River Lake (A) is materially cleaner than Lake Koshkonong (F). 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 — Rock River 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?
Lake Koshkonong
Very murky, less than 1.7 ft of visibility.
Rock River Lake
Crystal clear, you can see 21 ft down.
Side-by-Side Metrics
| Metric | Lake Koshkonong | Rock River Lake |
|---|---|---|
| Overall Grade | F (Very Poor) | A (Excellent) |
| Water Clarity | 1.7 ft | 21 ft |
| Phosphorus | 287 µg/L | No data |
| Chlorophyll-a (Algae) | No data | No data |
| Maximum Depth | 7 ft | - |
| Surface Area | 10.6K acres | 548 acres |
| Public Access | Unknown | Unknown |
| Fish Species | 0 | 0 |
| Trophic State | hypereutrophic | oligotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Rock River Lake wins on overall water quality with a Grade A versus Lake Koshkonong's Grade F. Water clarity: 21 ft vs 1.7 ft. For fishing diversity, Rock River Lake also leads with 0 species.