Sunnen Lake
Washington County, Missouri198 acresView mapDirections
Missouri DNR publishes the water-quality measurements for Sunnen Lake. Here is what has been measured.
- Impaired · Algal growth
- 72 ft max depth
- Limited data
Sunnen Lake in Washington County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 1 ft visibility. Phosphorus: 61 µg/L. Chlorophyll-a (algae): 14.3 µg/L. Surface area: 198 acres.
Sunnen Lake is a 198-acre lake in Washington County, Missouri with an estimated average depth of about 72 feet.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2023-08-16. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Sunnen Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
Whether Sunnen Lake is safe to swim in today is a call for the Missouri Department of Natural Resources and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Sunnen Lake
These are the measurements Missouri DNR publishes for Sunnen Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 1 ft of visibility. Phosphorus 61 µg/L. Chlorophyll-a 14.3 µg/L. TSI 66.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 61µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 14.3µg/L | Measured, not scored The green pigment in algae — a direct measure of how much algae is in the water. |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 66 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Sunnen Lake
Answers come straight from the public measurements and survey records on this page.
Lake Details
Max depth
~72 ft est.
Surface area
198 acres
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Missouri has not published bathymetry for Sunnen Lake.
Lake Size & Watershed
Watershed (drainage) area
27 sq mi
HydroLAKES / HydroSHEDS
Shoreline
3.4 mi
HydroLAKES / HydroSHEDS
Elevation
850 ft
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
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Fishing Sunnen Lake
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
Designated uses not supporting: Aquatic life.
Source: EPA ATTAINS assessment unit MO_7294.00 · Official waterbody report
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.
Nearby Lakes in Washington County
Frequently asked questions about Sunnen Lake
Where is Sunnen Lake?
- Sunnen Lake is a lake in Washington County, Missouri. Its water-quality measurements are published by Missouri DNR and shown on this page as reported.
What is the water quality of Sunnen Lake?
- Sunnen Lake in Washington County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 1 ft visibility. Phosphorus: 61 µg/L. Chlorophyll-a (algae): 14.3 µg/L. Surface area: 198 acres.
Is Sunnen Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Sunnen Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth. Check local advisories before you swim.
How deep is Sunnen Lake?
- No published bathymetric survey covers Sunnen Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 72 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate. The lake covers 198 acres.
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Where this data comes from
3 measurements from 1 monitoring station, 2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Missouri Dept. of Natural Resources
MDNR3 samples · 2023
Analytical methods
- Depth, Secchi disk in meters
- Nitrogen and Phosphorus, Total, Whole-water, Alkaline Persulfate Digest
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (1)
EPA condition classes from the National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See where the data comes from and data sources.
Other records on this page
Impairment status from EPA ATTAINS 303(d) database
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)