Where is Simpson Park Lake?

Simpson Park Lake 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 temperature of Simpson Park Lake?

Simpson Park Lake typically sits around 80°F at the surface in September, from 50 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.

How deep is Simpson Park Lake?

No published bathymetric survey covers Simpson Park Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 21 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.

Are there boat ramps on Simpson Park Lake?

Simpson Park Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Simpson Park Lake (East), Simpson Park Lake (West). Public access is listed as yes.

Can I fish at Simpson Park Lake?

Simpson Park Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Missouri's fish and wildlife agency, so check its current regulations before you go.

Simpson Park Lake

St. Louis County, MissouriView map Directions

Missouri DNR publishes the water-quality measurements for Simpson Park Lake. Here is what has been measured.

Clarity

1.9 ft

Murkier than most

Secchi · sampled 2024

Phosphorus

72.3 µg/L

More phosphorus than most

Measured by Missouri DNR

Chlorophyll-a

23.8 µg/L

Typical for Missouri

Measured by Missouri DNR

Water temp

~80°F

Typical for Sep · EPA WQP

Max depth

~21 ft est.

GLOBathy model

Type

Eutrophic

Trophic class

Eutrophic
Impaired · Algal growth
21 ft max depth
Public access

See the measurements Directions Where to stay

Simpson Park Lake in St. Louis County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 1.9 ft visibility. Phosphorus: 72.3 µg/L. Chlorophyll-a (algae): 23.8 µg/L.

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Simpson Park Lake is a productive, nutrient-rich eutrophic lake in St. Louis County, Missouri with an estimated average depth of about 21 feet. Overall water quality is improving over recent sampling years. Limited fish-species data available. Public access is available with 2 public boat landings. Compared to the 4 other monitored lakes in St. Louis County, Simpson Park Lake ranks #1 for water quality.

Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2024-09-20. Methodology: how these readings are compared.

Simpson Park Lake has 2 public boat landings, so a lakefront rental is not the only way to get a boat on the water. Vrbo is where to look for cabins and lake homes around Simpson Park Lake, and Booking.com and Expedia search hotels near the lake for your dates.

What Simpson Park Lake is good for

From access and monitoring records, not editorial picks.

Boat launch2 documented ramps

Swimming conditions

Readings only

Algae 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. Simpson Park Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, mercury. Check local advisories before you swim.

Whether Simpson Park 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.

Compare swimming lakes near St. Louis →

Get alerts for Simpson Park Lake →

Water quality measurements for Simpson Park Lake

These are the measurements Missouri DNR publishes for Simpson Park 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 1.9 ft of visibility. Phosphorus 72.3 µg/L. Chlorophyll-a 23.8 µg/L. TSI 65.

Water quality readings
Measure	Reading	Where it sits
Water clarity (Secchi depth)	1.9ft	Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer.
Total phosphorus	72.3µg/L	Poor GoodFairPoor
Chlorophyll-a (algae)	23.8µg/L	Poor GoodFairPoor
Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a.	65	Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic

High nutrients, frequent algae, reduced clarity

Ask about Simpson Park Lake

Answers come straight from the public measurements and survey records on this page.

Water Temperature

Simpson Park Lake typically sits around 80°F at the surface in September. Summer average is about 84°F. Usually warmest in Aug (about 85°F) and coldest in Apr (about 66°F). These are typical values by month — not a live reading.

Jan

Feb

Mar

66°

Apr

72°

May

83°

Jun

84°

Jul

85°

Aug

80°

Sep

Oct

Nov

Dec

Column height runs from this lake’s coldest month (66°F) to its warmest (85°F).

Typical surface water temperature by month, from 50 field readings (2010–2024) via the EPA Water Quality Portal. See the full Simpson Park Lake water temperature breakdown →

Lake Details

Max depth

~21 ft est.

Public access

Yes

Listed by Missouri DNR

Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Missouri has not published bathymetry for Simpson Park Lake.

Lake Size & Watershed

Watershed (drainage) area

3,856 sq mi

HydroLAKES / HydroSHEDS

Surface area

59 acres

HydroLAKES / HydroSHEDS

Shoreline

1.1 mi

HydroLAKES / HydroSHEDS

Elevation

400 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.

Recreation & Access

Boat Landings

Yes

Public Access

Simpson Park Lake (East)Public
Simpson Park Lake (West)Public

Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps

Stays via Stay22

Stays near Simpson Park Lake

Compare lakeside cabins, hotels, and vacation rentals near Simpson Park Lake in St. Louis 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 Simpson Park Lake are listed below.

Top-rated places to stay near Simpson Park Lake

Prices for Oct 23–25, 4 adults. Change dates on the map below.

Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.

Planning a whole trip? See where to stay at Missouri’s top lakes →

Follow Simpson Park Lake’s readings

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Fishing Simpson Park Lake

→ Simpson Park Lake fishing regulations (limits, seasons, special rules)

Water Quality Trend: Improving

Based on 4 years of monitoring (2020–2024).

Water clarity
Stable
4 years
Phosphorus
Improving
-3.9 µg/L/yr4 years
Chlorophyll-a
Stable
-0.42 µg/L/yr4 years

See year-by-year chart →

EPA Impairment Status

Simpson Park Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).

Causes of impairment

Algal growthMercury

Designated uses not supporting: Aquatic life, Fish consumption.

Source: EPA ATTAINS assessment unit MO_7502.00 · Official waterbody report

Regulated Pollution Sources Nearby

22 EPA-permitted facilities operate within about 5 miles of Simpson Park Lake under Clean Water Act (NPDES) discharge permits. 1 facility has a reported Clean Water Act violation in the past three years.

Mdc, Powder Valley Nature Center
Kirkwood · 1.9 mi away · NPDES MO0109975
Recent violation
Bohn And Dawson, Incorporated
St. Louis · 0.3 mi away · NPDES MONX00752
Bohn And Dawson, Inc.
Kirkwood · 0.3 mi away · NPDES MO0001627
Basf Agricultural Solutions Us Llc
St. Louis · 0.4 mi away · NPDES MONX00689
Daimler Chrysler St. Loui
Fenton · 0.5 mi away · NPDES MO0000167
Bausch And Lomb
St. Louis · 0.5 mi away · NPDES MONX00077

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

Tilles Park Reservoir7.1 miView →Mallard Lake1.9 ft clear · Hypereutrophic10.1 miView →Creve Coeur Lake1.6 ft clear · Hypereutrophic10.7 miView →Bee Tree Lake—View →Koeneman Park Lake3.1 ft clear · Hypereutrophic—View →Spanish Lake1.6 ft clear · Hypereutrophic—View →

Frequently asked questions about Simpson Park Lake

Where is Simpson Park Lake?: Simpson Park Lake 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 Simpson Park Lake?: Simpson Park Lake in St. Louis County, Missouri has water-quality measurements published by Missouri DNR, shown here as reported. Water clarity: 1.9 ft visibility. Phosphorus: 72.3 µg/L. Chlorophyll-a (algae): 23.8 µg/L.
Is Simpson Park Lake safe to swim in?: Nutrient and algae readings are not a swimming clearance. Simpson Park Lake is listed impaired under Clean Water Act §303(d) (IR 5) for algal growth, mercury. Check local advisories before you swim.
What is the water temperature of Simpson Park Lake?: Simpson Park Lake typically sits around 80°F at the surface in September, from 50 EPA Water Quality Portal field readings (2010–2024). That is a typical value for the month, not a live reading.
How deep is Simpson Park Lake?: No published bathymetric survey covers Simpson Park Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 21 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Simpson Park Lake?: Simpson Park Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Named access points include Simpson Park Lake (East), Simpson Park Lake (West). Public access is listed as yes.
Can I fish at Simpson Park Lake?: Simpson Park Lake has 2 documented boat landings in the USGS National Boat Ramps inventory. Seasons, size and bag limits, and whether you need a license are set by Missouri's fish and wildlife agency, so check its current regulations before you go.

Explore Simpson Park Lake across LakeQuality

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Species activity outlook by water temperature and season

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Planning a trip around Gateway Arch?

Simpson Park Lake is about 16 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 →

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Where this data comes from

86 measurements from 2 monitoring stations, 2020–2024. Retrieved from the EPA Water Quality Portal on 2026-08-02.

Collected and reported by

Univ. of Missouri, ColumbiaUMC83 samples · 2020–2024
Missouri Dept. of Natural ResourcesMDNR3 samples · 2021

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
Nitrogen and Phosphorus, Total, Whole-water, Alkaline Persulfate Digest

Monitoring station identifiers (2)

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.