Mesotrophic Lakes in Iowa
12 mesotrophic lakes in Iowa. Moderate nutrients, good water quality.
Most well-managed working lakes register as mesotrophic — the band that balances productivity with clarity. 12 lakes in Iowa sit in the mesotrophic band. About 0% are deep (50+ ft); the rest are shallower basins where watershed management keeps nutrients from pushing the system into eutrophy.
Mesotrophic lakes tend to grade B or C on the LakeGrade rubric — the productive-but-clear band lines up with the middle of the letter grades.
| # | Lake | County | Grade | Clarity | Depth | TSI |
|---|---|---|---|---|---|---|
| 1 | Blue Pit Lake | Cerro Gordo | A | 17.1 ft | - | 40 |
| 2 | Nine Eagles Lake | Decatur | A | 11 ft | - | 43 |
| 3 | Terra Park Lake | Polk | A | 11.5 ft | - | 44 |
| 4 | Dale Maffitt Reservoir | Dallas | B | 9.8 ft | - | 42 |
| 5 | Rudd Lake | Floyd | B | 8.1 ft | - | 46 |
| 6 | Slipbluff Lake | Decatur | B | 9 ft | - | 45 |
| 7 | Lacey Keosauqua Lake | Van Buren | B | 7.1 ft | - | 47 |
| 8 | Yenruogis Pond | Keokuk | B | 9.9 ft | - | 46 |
| 9 | Ada Hayden Heritage Park Lake | Story | B | 6.8 ft | - | 48 |
| 10 | Lambach Lake | Scott | B | 7.9 ft | - | 47 |
| 11 | Sand Lake | Marshall | B | 6.4 ft | - | 47 |
| 12 | Little Sioux Park Lake | Woodbury | C | 5.7 ft | - | 50 |
All mesotrophic lakes →Minnesota version →Wisconsin version →Illinois version →Michigan version →Ohio version →Pennsylvania version →New York version →Missouri version →Indiana version →North Dakota version →South Dakota version →All Iowa lakes →
Source: EPA National Aquatic Resource Surveys, 2026.