Delaware County Lake Quality
Ohio, 4 lakes, average grade D (Poor)
Delaware County has 4 graded lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. On average, Delaware County lakes grade D, with phosphorus loading and reduced clarity showing up across most of the dataset.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Alum Creek Lake (A); the most-stressed is Alum Creek Lake (F).
Quick Answers for Delaware County
Planning a trip? Check special fishing regulations for Alum Creek Lake — or check the official Ohio fishing regulations.
All Lakes in Delaware County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Alum Creek Lake | A | - | 37.1 µg/L |
| 2 | Alum Creek Lake | F | - | 80.6 µg/L |
| 3 | O'Shaughnessy Reservoir Lake | F | - | 157 µg/L |
| 4 | Hoover Reservoir | F | - | 168 µg/L |
Other Counties in Ohio
See how Delaware County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 36 states and 2 Canadian provinces.
Where to stay near Delaware County
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Source: EPA National Aquatic Resource Surveys, 2026.