Green Castle Lake vs Union Grove Lake
Water quality, depth, fish species, and recreation comparison.
Green Castle Lake has a higher water quality grade (C, Fair) than Union Grove Lake (F, Very Poor). Both are in Wisconsin.
Green Castle Lake and Union Grove Lake are both in Iowa — 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 meaningfully apart: Green Castle Lake grades a C while Union Grove Lake grades a F. 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 — Green Castle 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?
Green Castle Lake
Murky, only visible to about 4.6 ft.
Union Grove Lake
Very murky, less than 1.6 ft of visibility.
Side-by-Side Metrics
| Metric | Green Castle Lake | Union Grove Lake |
|---|---|---|
| Overall Grade | C (Fair) | F (Very Poor) |
| Water Clarity | 4.6 ft | 1.6 ft |
| Phosphorus | No data | No data |
| Chlorophyll-a (Algae) | 6.9 µg/L | 88.5 µg/L |
| Maximum Depth | - | - |
| Surface Area | 17 acres | 117 acres |
| Public Access | Unknown | Unknown |
| Fish Species | 0 | 0 |
| Trophic State | eutrophic | hypereutrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Green Castle Lake wins on overall water quality with a Grade C versus Union Grove Lake's Grade F. Water clarity: 4.6 ft vs 1.6 ft. For fishing diversity, Green Castle Lake also leads with 0 species.