Tilles Park Reservoir
St. Louis County, MissouriView mapDirections
Missouri DNR publishes the water-quality measurements for Tilles Park Reservoir. Here is what has been measured.
- Limited data
Tilles Park Reservoir in St. Louis County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Phosphorus: 434.5 µg/L. Chlorophyll-a (algae): 66.5 µg/L.
Tilles Park Reservoir is a lake in St. Louis County, Missouri.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2022-06-05. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Tilles Park Reservoir 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 Tilles Park Reservoir
These are the measurements Missouri DNR publishes for Tilles Park Reservoir, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 434.5 µg/L. Chlorophyll-a 66.5 µg/L. TSI 82.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 435µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| Chlorophyll-a (algae) | 66.5µg/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. | 82 | Hypereutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Very high nutrients, dense algae, poor clarity
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Fishing Tilles Park Reservoir
Regulated Pollution Sources Nearby
24 EPA-permitted facilities operate within about 5 miles of Tilles Park Reservoir under Clean Water Act (NPDES) discharge permits. 2 facilities have a reported Clean Water Act violation in the past three years.
- Rock Hill Quarries Company Demo LandfillSt. Louis · 0.5 mi away · NPDES MO0138371Recent violation
- Mo Petroleum ProductsOverland · 4.3 mi away · NPDES MO0126357Recent violation
- Rock Hill Fire DepartmentRock Hill · 1 mi away · NPDES MONX00802
- Rock Hill Public Works DepartmentRock Hill · 1.1 mi away · NPDES MONX00799
- Service Center Webster GrovesWebster Groves · 1.3 mi away · NPDES MONX00061
- Specgx LlcWebster Groves · 1.5 mi away · NPDES MONX00257
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 St. Louis County
Frequently asked questions about Tilles Park Reservoir
Where is Tilles Park Reservoir?
- Tilles Park Reservoir is a lake in St. Louis County, Missouri. Its water-quality measurements are published by Missouri DNR and shown on this page as reported.
What is the water quality of Tilles Park Reservoir?
- Tilles Park Reservoir in St. Louis County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Phosphorus: 434.5 µg/L. Chlorophyll-a (algae): 66.5 µg/L.
Is Tilles Park Reservoir safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Explore Tilles Park Reservoir across LakeQuality
Planning a trip around Gateway Arch?
Tilles Park Reservoir is about 9 miles from Gateway Arch National Park. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Gateway Arch →More lakes in Missouri
Other Lakes in Missouri
Hypereutrophic Lakes in Missouri
Where this data comes from
6 measurements from 1 monitoring station, 2022. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Univ. of Missouri, Columbia
UMC6 samples · 2022
Analytical methods
- 4500 P E ~ Phosphorus in Water by Colorimetry- Ascorbic Acid Method
- 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
Regulated discharger data from EPA ECHO (ICIS-NPDES)