Where is Simpson Park Lake?

Simpson Park Lake is a lake in St. Louis County, Missouri. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.

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.

Simpson Park Lake

St. Louis County, MissouriView map Directions

Nutrient-rich

Nutrients and algae run above the regional average.

Water temp

~80°F

Typical for Sep · EPA WQP

Clarity

1.9 ft

Secchi · sampled 2024

Max depth

~21 ft est.

GLOBathy model

Level

No gauge

Trend

Improving

4 years of samples

Eutrophic
Impaired · Algal growth
#1 of 5 in the county
21 ft max depth
Public access

See the measurements Directions Where to stay

Simpson Park Lake in St. Louis County, Missouri has a water quality grade of D (Nutrient-rich). Water clarity: 1.9 ft visibility. Phosphorus: 72.3 µg/L. Chlorophyll-a (algae): 23.8 µg/L.

Clarity: 1.9 ft
Typical in September: 80°F
Max depth: ~21 ft est.
Type: Eutrophic
Phosphorus: 72.3 µg/L
Chlorophyll-a: 23.8 µg/L
Trend: ↑ Improving
Public access: Yes

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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 grade measures 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 Sep 11–13, 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 →

Watch Simpson Park Lake’s letter

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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. Water quality is graded D based on 2 sampling years through 2024. 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. Grade methodology: LakeQuality methodology.

What Simpson Park Lake is good for

From access and monitoring records, not editorial picks.

Boat launch2 documented ramps

Swimming Safety

Grade only

Algae risk

Based on clarity and algae grades from past sampling — we do not hold live water temperature and a current cyanobacteria reading for this lake. Check your state or county health department before you swim.

The D is nutrients and algae, 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.

Compare the safest swimming lakes near St. Louis →

Get alerts for Simpson Park Lake →

Water Quality Grade: D (Nutrient-rich)

Very murky, less than 1.9 ft of visibility. Phosphorus 72.3 µg/L. Chlorophyll-a 23.8 µg/L. TSI 65. The letter is not a swimming clearance.

Metric	Value	Grade
Water Clarity (Secchi Depth)	1.9 ft	Not graded
Phosphorus	72.3 µg/L	Poor
Chlorophyll-a (Algae)	23.8 µg/L	Poor
Trophic State Index (TSI)	65	Eutrophic

High nutrients, frequent algae, reduced clarity

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

—

Apr

66°

May

72°

Jun

83°

Jul

84°

Aug

85°

Sep

80°

Oct

—

Nov

—

Dec

—

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

Characteristic	Value
Maximum Depth	~21 ft est.
Average Depth	~10 ft est.
Public Access	Yes

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

Surface area

59 acres

Shoreline

1.1 mi

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

Fishing Simpson Park Lake

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

Water Quality Trend: ↑ Improving

Based on 4 years of monitoring data (2020-2025).

Metric	Trend	Change/Year	Years
Water Clarity	→ Stable	-0.004 m/yr	4
Phosphorus	↑ Improving	-3.9 µg/L/yr	4
Chlorophyll-a	→ Stable	-0.42 µg/L/yr	4

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

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.

County Ranking

Ranked #1 of 5 lakes in St. Louis County

Nearby Lakes in St. Louis County

NRTilles Park Reservoir7.1 miView →FMallard Lake1.9 ft clear · Hypereutrophic10.1 miView →FCreve Coeur Lake1.6 ft clear · Hypereutrophic10.7 miView →NRBee Tree Lake—View →FKoeneman Park Lake3.1 ft clear · Hypereutrophic—View →FSpanish 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. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Simpson Park Lake?: Simpson Park Lake in St. Louis County, Missouri has a water quality grade of D (Nutrient-rich). 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?: The D is nutrients and algae, 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.

Explore Simpson Park Lake across LakeQuality

Lake Fishing Forecast

Species activity outlook by water temperature and season

Missouri Lake Trips

Where to stay at Missouri's top lakes, each with its grade

Eutrophic Lakes

High nutrients, frequent algae, reduced clarity

The State of Missouri's Lakes

Missouri's cleanest and most-polluted lakes, ranked

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 →

More Missouri Lake Rankings

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Ranked by overall water quality grade

Clearest lakes in Missouri

Top 25 by Secchi water clarity

Best swimming lakes in Missouri

Grade A/B + low algae filter

Family fishing lakes in Missouri

Panfish-rich, public access

All Missouri lakes

Full state directory

Other Grade D Lakes in Missouri

Forest Park Pond

St. Louis city County · 1.6 ft

Boathouse Lake

St. Louis city County · 2.3 ft

Lafayette Park Lake

St. Louis city County · 2.3 ft

Lake Serene

Franklin County · 2.6 ft

Callaway Fork Lake

St. Charles County · 2.1 ft

Robin Hood Lake

Warren County · 3 ft

Eutrophic Lakes in Missouri

Forest Park Pond Boathouse Lake Jefferson Lake Lafayette Park Lake

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)

Grade thresholds from the EPA National Lakes Assessment (EPA 841-R-24-006, Table 6-3), applied by ecoregion. See how grades are calculated 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)

Named boat-access points from the USGS National Boat Ramps inventory