Marion Reservoir is a 7-acre mesotrophic lake in Franklin County, Missouri. Water quality is graded B based on 3 sampling years through 2021. Compared to the 4 other monitored lakes in Franklin County, Marion Reservoir ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2021-08-14. Grade methodology: LakeGrade methodology.
Watch Marion Reservoir water quality
Subscribe for LakeQuality updates by email. No spam, unsubscribe anytime.
Swimming Safety
Good for swimming, clear water with low algae levels
Water Quality Grade: B, Good
Murky, only visible to about 5.9 ft. Phosphorus level: 16 µg/L. Chlorophyll-a: 9.8 µg/L. Trophic State Index: 50.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.9 ft | D |
| Phosphorus | 16 µg/L | A |
| Chlorophyll-a (Algae) | 9.8 µg/L | B |
| Trophic State Index (TSI) | 50 | Mesotrophic |
Moderate nutrients, good water quality
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 7 acres |
Where to stay near Marion Reservoir
Compare lakeside cabins, hotels, and vacation rentals near Marion Reservoir in Franklin County, Missouri — live availability and prices for your trip. Switch the map to Satellite to see the lake and how close each stay is to the water.
Top-rated places to stay near Marion Reservoir
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 Marion Reservoir?
Get lake water-quality report cards plus the best cabin & lodging deals near Marion Reservoir — straight to your inbox. No spam, unsubscribe anytime.
Planning a whole trip? See where to stay at Missouri’s top lakes →
Fishing Marion Reservoir
Location
County Ranking
Ranked #1 of 5 lakes in Franklin County
Cleaner Lakes Within 30 Miles
Marion Reservoir holds Grade B. One nearby lake has a higher grade.
See full comparison →Nearby Lakes in Franklin County
Explore Marion Reservoir across LakeGrade
More Missouri Lake Rankings
Other Grade B Lakes in Missouri
Mesotrophic Lakes in Missouri
More records, surveys & data sources
Reservoir Info (USACE NID)
Marion Reservoir is a man-made reservoir impounded by the Lake Marion Dam (completed 1965), built primarily for recreation on the TR TO CLAVEY CREEK; earth-type dam, 30 ft tall.
- Surface area
- 7 ac
- Normal storage
- 70 ac-ft
- Max storage
- 112 ac-ft
- Drainage area
- 100 sq mi
- Hazard class
- Low
- Owner
- CALVEY LAKE SUBDV HMOWNS
Source: USACE National Inventory of Dams, NID ID MO30571 · Operator website
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Marion Reservoir under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Calvey Brook Estates WwtpRobertsville · 3.2 mi away · NPDES MO0130095Recent violation
Facilities permitted to discharge under the Clean Water Act within ~5 miles; proximity does not by itself mean a facility affects this lake. Source: EPA ECHO (ICIS-NPDES), as of 2026-07.
Data Sources
Water quality data from the EPA Water Quality Portal
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2021-08-14
Monitoring stations: 1