Boathouse Lake
St. Louis city County, MissouriView mapDirections
Missouri DNR publishes the water-quality measurements for Boathouse Lake. Here is what has been measured.
- Eutrophic
Boathouse Lake in St. Louis city County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 2.3 ft visibility. Phosphorus: 59.8 µg/L. Chlorophyll-a (algae): 18 µg/L.
Boathouse Lake is a productive, nutrient-rich eutrophic lake in St. Louis city County, Missouri. Phosphorus level is improving over recent sampling years. Compared to the 2 other monitored lakes in St. Louis city County, Boathouse Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2024-09-11. Methodology: how these readings are compared.
Swimming conditions
Readings onlyAlgae risk
Based on clarity and algae readings from past sampling — there is no live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether Boathouse 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 Boathouse Lake
These are the measurements Missouri DNR publishes for Boathouse 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 2.3 ft of visibility. Phosphorus 59.8 µg/L. Chlorophyll-a 18 µg/L. TSI 62.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.3ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 59.8µg/L | Poor GoodFairPoor |
| Chlorophyll-a (algae) | 18µg/L | Fair GoodFairPoor |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 62 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Boathouse Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Boathouse Lake typically sits around 80°F at the surface in September. Summer average is about 83°F. Usually warmest in Jul (about 84°F) and coldest in Apr (about 62°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (62°F) to its warmest (84°F).
Typical surface water temperature by month, from 48 field readings (2019–2024) via the EPA Water Quality Portal. See the full Boathouse Lake water temperature breakdown →
Stays via Stay22
Stays near Boathouse Lake
Compare lakeside cabins, hotels, and vacation rentals near Boathouse Lake in St. Louis city 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. The water-quality readings cover nutrients and algae, not lodging. Cabins and rentals around Boathouse Lake are listed below.
Top-rated places to stay near Boathouse Lake
Prices for Oct 30–Nov 1, 4 adults. Change dates on the map below.
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Planning a whole trip? See where to stay at Missouri’s top lakes →
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Fishing Boathouse Lake
Water Quality Trend: Stable
Based on 5 years of monitoring (2020–2024).
Water clarity
Stable5 years
Phosphorus
Improving-1.45 µg/L/yr5 years
Chlorophyll-a
Worsening+3.12 µg/L/yr5 years
Regulated Pollution Sources Nearby
12 EPA-permitted facilities operate within about 5 miles of Boathouse Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 4 facilities have a reported Clean Water Act violation in the past three years.
- Msd Lemay WwtpSt. Louis · 2.7 mi away · NPDES MO0025151Major
- Dupo Stp, Village OfDupo · 1.7 mi away · NPDES IL0026441Recent violation
- Acbl Transportation Services LlcSt. Louis · 1.7 mi away · NPDES MO0001601Recent violation
- American River TransportSt. Louis · 2 mi away · NPDES MO0138975Recent violation
- Dupo TerminalDupo · 4.2 mi away · NPDES IL0045284Recent violation
- Mdanda Turbine Generator Repair FacilitySt Louis · 1.1 mi away · NPDES MONX00812
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 city County
Frequently asked questions about Boathouse Lake
Where is Boathouse Lake?
- Boathouse Lake is a lake in St. Louis city County, Missouri. Its water-quality measurements are published by Missouri DNR and shown on this page as reported.
What is the water quality of Boathouse Lake?
- Boathouse Lake in St. Louis city County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 2.3 ft visibility. Phosphorus: 59.8 µg/L. Chlorophyll-a (algae): 18 µg/L.
Is Boathouse Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
What is the water temperature of Boathouse Lake?
- Boathouse Lake typically sits around 80°F at the surface in September, from 48 EPA Water Quality Portal field readings (2019–2024). That is a typical value for the month, not a live reading.
Explore Boathouse Lake across LakeQuality
Planning a trip around Gateway Arch?
Boathouse Lake is about 6 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
Eutrophic Lakes in Missouri
Where this data comes from
105 measurements from 1 monitoring station, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Univ. of Missouri, Columbia
UMC105 samples · 2020–2024
Analytical methods
- Depth, Secchi disk in meters
- 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)