Franklin County Lake Quality
Missouri, 5 lakes, average grade C (Fair)
Only 5 lakes in Franklin County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. The county average is C — the middle of the rubric, with one or two lakes pulling the average up or down depending on year.
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 Marion Reservoir (B); the most-stressed is Foxboro Lake (D).
Quick Answers for Franklin County
Planning a trip? Check special fishing regulations for Marion Reservoir — or check the official Missouri fishing regulations.
All Lakes in Franklin County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Marion Reservoir | B | 5.9 ft | 16 µg/L |
| 2 | Port Hudson Lake | C | 6.1 ft | 20.8 µg/L |
| 3 | Fawn Lake | C | 3.6 ft | 30 µg/L |
| 4 | Lake Serene | D | 2.6 ft | 39.5 µg/L |
| 5 | Foxboro Lake | D | 4 ft | - |
Other Counties in Missouri
See how Franklin County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 17 states.
Where to stay near Franklin County
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Source: EPA National Aquatic Resource Surveys, 2026.