L. Ste. Louise Lake is a 70-acre productive, nutrient-rich eutrophic lake in St. Charles County, Missouri. Water quality is graded D based on 3 sampling years through 2024. Overall water quality is declining over recent sampling years. Compared to the 10 other monitored lakes in St. Charles County, L. Ste. Louise Lake ranks #4 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2024-09-15. 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 2.6 ft of visibility. Phosphorus level: 40.8 µg/L. Chlorophyll-a: 18.3 µg/L. Trophic State Index: 60.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | F |
| Phosphorus | 40.8 µg/L | C |
| Chlorophyll-a (Algae) | 18.3 µg/L | C |
| Trophic State Index (TSI) | 60 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 70 acres |
Where to stay near L. Ste. Louise Lake
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Fishing L. Ste. Louise Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.03 m/yr | 5 |
| Phosphorus | → Stable | -0.47 µg/L/yr | 5 |
| Chlorophyll-a | ↓ Declining | +1.19 µg/L/yr | 5 |
Water Temperature
L. Ste. Louise Lake averages about 82°F at the surface in summer, usually warmest in Jul (about 84°F) and coldest in Apr (about 64°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 83 field readings (2015–2024) via the EPA Water Quality Portal.
Location
County Ranking
Ranked #4 of 11 lakes in St. Charles County
Nearby Lakes in St. Charles County
Explore L. Ste. Louise 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)
L. Ste. Louise Lake is a man-made reservoir impounded by the Lake Sainte Louise Dam (completed 1967), built primarily for recreation on the BRANCH PERUQUE CREEK; earth-type dam, 52 ft tall and 790 ft long.
- Surface area
- 70 ac
- Normal storage
- 1,170 ac-ft
- Max storage
- 1,420 ac-ft
- Drainage area
- 1.04 sq mi
- Hazard class
- High
- Owner
- LAKE SAINT LOUIS COMM.
Source: USACE National Inventory of Dams, NID ID MO10490 · Operator website · Matched by proximity (0.83 km)
EPA Impairment Status
L. Ste. Louise 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_7055.00 · Official waterbody report · Matched by proximity (0.22 km)
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
9 EPA-permitted facilities operate within about 5 miles of L. Ste. Louise Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.
- General Motors Wentzville Assembly CntrWentzville · 1.4 mi away · NPDES MO0100153Recent violation
- Blastco IncWentzville · 0.8 mi away · NPDES MO0095818
- Lear CorporationWentzville · 2.2 mi away · NPDES MONX00614
- Dubois Chemicals WentzvilleWentzville · 2.3 mi away · NPDES MONX00778
- Marine Technology IncWentzville · 2.5 mi away · NPDES MONX00994
- Lear CorporationWentzville · 2.6 mi away · NPDES MONX00840
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: 2024-09-15
Monitoring stations: 1