Corydon Reservoir vs Lake Marie
Water quality, depth, fish species, and recreation comparison.
Lake Marie has a higher water quality grade (B, Good) than Corydon Reservoir (F, Very Poor).
Corydon Reservoir is in Iowa; Lake Marie is in Missouri. Cross-state comparisons carry an extra wrinkle — Minnesota PCA and Wisconsin DNR use slightly different sampling cadences and station coverage, though both feed the same EPA Water Quality Portal. Lake Marie (B) is materially cleaner than Corydon Reservoir (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 — Lake Marie 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?
Corydon Reservoir
Very murky, less than 1.9 ft of visibility.
Lake Marie
Moderate clarity, visible to about 7.8 ft.
Side-by-Side Metrics
| Metric | Corydon Reservoir | Lake Marie |
|---|---|---|
| Overall Grade | F (Very Poor) | B (Good) |
| Water Clarity | 1.9 ft | 7.8 ft |
| Phosphorus | No data | 13 µg/L |
| Chlorophyll-a (Algae) | 44 µg/L | 2.7 µg/L |
| Maximum Depth | - | - |
| Surface Area | 66.9 acres | 30 acres |
| Public Access | Unknown | Unknown |
| Fish Species | 0 | 0 |
| Trophic State | eutrophic | mesotrophic |
Bold value = better for that metric (lower phosphorus / chlorophyll = cleaner; higher Secchi / depth / species count = better).
Verdict
Lake Marie wins on overall water quality with a Grade B versus Corydon Reservoir's Grade F. Water clarity: 7.8 ft vs 1.9 ft. For fishing diversity, Lake Marie also leads with 0 species.