Franklin County Lake Quality
Missouri, 5 lakes, average grade C (Fair)
Franklin County holds 5 monitored lakes. With a sample that small the county-level summary describes those specific waters, not necessarily every water body in the county. 3 of those lakes carry an A–F grade. The county-level summary describes that subset, not every water body listed. Franklin County averages to a C. The distribution behind that average matters more than the letter: a few stressed lakes versus many decent ones can produce the same average as the inverse.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Port Hudson Lake (C) is the cleanest in the county.
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Quick Answers for Franklin County
Planning a trip? Check special fishing regulations for Port Hudson Lake — or check the official Missouri fishing regulations.
All Lakes in Franklin County
5 lakes · 3 graded, 2 not rated3 graded lakes · 2 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | CPort Hudson LakeFranklin | C | 6.1 ft | 20.8 µg/L | 7.5 µg/L | No recent samples | ✓ Public |
| 2 | CFawn LakeFranklin | C | 3.6 ft | 30 µg/L | 10.8 µg/L | No recent samples | Not recorded |
| 3 | DLake SereneFranklin | D | 2.6 ft | 39.5 µg/L | 13.6 µg/L | No recent samples | ✓ Public |
| NRFoxboro LakeFranklin | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRMarion ReservoirFranklin | NR | 5.9 ft | 16 µg/L | 9.8 µg/L | No recent samples | Not recorded |
NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
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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 49 states and 2 Canadian provinces.
Source: EPA National Aquatic Resource Surveys, 2026.