Sunnen Lake is a 198-acre productive, nutrient-rich eutrophic lake in Washington County, Missouri. Water quality is graded D based on 3 sampling years through 2023. Compared to the 1 other monitored lakes in Washington County, Sunnen Lake ranks #2 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2023-08-16. Grade methodology: LakeGrade methodology.
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Swimming Safety
Swimming not recommended, poor water quality with high algae risk
Water Quality Grade: D, Poor
Very murky, less than 1 ft of visibility. Phosphorus level: 61 µg/L. Chlorophyll-a: 14.3 µg/L. Trophic State Index: 66.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1 ft | F |
| Phosphorus | 61 µg/L | D |
| Chlorophyll-a (Algae) | 14.3 µg/L | C |
| Trophic State Index (TSI) | 66 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 198 acres |
Where to stay near Sunnen Lake
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Fishing Sunnen Lake
Location
County Ranking
Ranked #2 of 2 lakes in Washington County
Cleaner Lakes Within 30 Miles
Sunnen Lake holds Grade D. 5 nearby lakes hold higher grades.
- ALake CapriSt. Francois County · 16.8 mi · Two grade letters higher (D → A)
- ACouncil Bluff LakeIron County · 15.4 mi · Two grade letters higher (D → A)
- ALake Shayne-Terre du Lac LakesWashington County · 16 mi · Two grade letters higher (D → A)
- ALake Marseilles-Terre du Lac LakesSt. Francois County · 17.1 mi · Two grade letters higher (D → A)
- ATimberline LakesSt. Francois County · 21.2 mi · Two grade letters higher (D → A)
Nearby Lakes in Washington County
Explore Sunnen Lake across LakeGrade
More Missouri Lake Rankings
Other Grade D Lakes in Missouri
Eutrophic Lakes in Missouri
More records, surveys & data sources
Reservoir Info (USACE NID)
Sunnen Lake is a man-made reservoir impounded by the Sunnen Dam (completed 1948), built primarily for recreation on the FOURCHE A RENAULT; earth-type dam, 51 ft tall and 1,300 ft long.
- Surface area
- 198 ac
- Normal storage
- 2,540 ac-ft
- Max storage
- 5,000 ac-ft
- Drainage area
- 26.85 sq mi
- Hazard class
- High
- Owner
- YMCA of the Ozarks
Source: USACE National Inventory of Dams, NID ID MO30111 · Operator website
EPA Impairment Status
Sunnen Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit MO_7294.00 · Official waterbody report
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
3 EPA-permitted facilities operate within about 5 miles of Sunnen Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- Village Inn Trailer Court WwtpPotosi · 4.8 mi away · NPDES MO0123765Recent violation
- Ymca Of The Ozarks WwtfPotosi · 0.1 mi away · NPDES MO0127922
- Shirley SchoolPotosi · 2.6 mi away · NPDES MO0083810
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
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Most recent sample: 2023-08-16
Monitoring stations: 1