St. Charles County Lake Quality
Missouri, 11 lakes, average grade D (Poor)
Only 11 lakes in St. Charles 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. On average, St. Charles 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 Callaway Fork Lake (D); the most-stressed is Kruse Lake (F).
Quick Answers for St. Charles County
Planning a trip? Check special fishing regulations for Callaway Fork Lake — or check the official Missouri fishing regulations.
All Lakes in St. Charles County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Callaway Fork Lake | D | 3.3 ft | 39.5 µg/L |
| 2 | L. Ste. Louise Lake | D | 3.2 ft | 33.5 µg/L |
| 3 | L. Ste. Louise Lake | D | 2.6 ft | 40.8 µg/L |
| 4 | Callaway Fork Lake | D | 2.1 ft | 78.5 µg/L |
| 5 | Lake St. Louis | D | 2.7 ft | 50 µg/L |
| 6 | Lake St. Louis by Dam | F | 2.3 ft | 74.8 µg/L |
| 7 | Kruse Lake | F | 2.6 ft | - |
Other Counties in Missouri
See how St. Charles County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 15 states.
Where to stay near St. Charles County
Top-rated places to stay near St. Charles County
Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.
Planning a trip to St. Charles County?
Get lake water-quality report cards plus the best cabin & lodging deals near St. Charles County — straight to your inbox. No spam, unsubscribe anytime.
Source: EPA National Aquatic Resource Surveys, 2026.