Delavan Lake vs Geneva Lake
Water quality, depth, fish species, and recreation comparison.
Geneva Lake has a higher water quality grade (A, Excellent) than Delavan Lake (C, Fair). Both are in Walworth County, Wisconsin.
Delavan Lake and Geneva 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 meaningfully apart: Geneva Lake grades a A while Delavan Lake grades a C. 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 — Geneva 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?
Delavan Lake
Moderate clarity, visible to about 8.9 ft.
Geneva Lake
Crystal clear, you can see 21 ft down.
Side-by-Side Metrics
| Metric | Delavan Lake | Geneva Lake |
|---|---|---|
| Overall Grade | C (Fair) | A (Excellent) |
| Water Clarity | 8.9 ft | 21 ft |
| Phosphorus | 52.5 µg/L | 13 µg/L |
| Chlorophyll-a (Algae) | 9.1 µg/L | 2.1 µg/L |
| Maximum Depth | 52 ft | 135 ft |
| Surface Area | 1,906 acres | 5,401 acres |
| Public Access | Yes | Yes |
| Fish Species | 6 | 6 |
| Trophic State | eutrophic | oligotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Geneva Lake wins on overall water quality with a Grade A versus Delavan Lake's Grade C. Water clarity: 21 ft vs 8.9 ft. For fishing diversity, Geneva Lake also leads with 6 species.
Source: EPA National Aquatic Resource Surveys, 2026.