Spanish Lake is a highly nutrient-loaded hypereutrophic lake in St. Louis County, Missouri. Water quality is graded F based on 3 sampling years through 2024. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 3 public boat landings. Compared to the 8 other monitored lakes in St. Louis County, Spanish Lake ranks #6 for water quality.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2024-09-21. Grade methodology: LakeGrade methodology.
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Swimming Safety
Avoid swimming, very poor water quality, potential algae toxins
Water Quality Grade: F, Very Poor
Very murky, less than 1.6 ft of visibility. Phosphorus level: 347.8 µg/L. Chlorophyll-a: 62.6 µg/L. Trophic State Index: 77.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.6 ft | F |
| Phosphorus | 347.8 µg/L | F |
| Chlorophyll-a (Algae) | 62.6 µg/L | F |
| Trophic State Index (TSI) | 77 | Hypereutrophic |
Very high nutrients, dense algae, poor clarity
Where to stay near Spanish Lake
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Fishing Spanish Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.01 m/yr | 5 |
| Phosphorus | ↓ Declining | +16.19 µg/L/yr | 5 |
| Chlorophyll-a | ↓ Declining | +14.35 µg/L/yr | 5 |
Recreation & Access
Water Temperature
Spanish Lake averages about 84°F at the surface in summer, usually warmest in Jul (about 85°F) and coldest in Apr (about 65°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 38 field readings (2020–2024) via the EPA Water Quality Portal. See the full Spanish Lake water temperature breakdown →
Location
County Ranking
Ranked #6 of 9 lakes in St. Louis County
Cleaner Lakes Within 30 Miles
Spanish Lake holds Grade F. 4 nearby lakes hold higher grades.
- DO'Fallon Park LakeSt. Louis city County · 8.4 mi · Higher grade (F → D)
- DForest Park PondSt. Louis city County · 11.9 mi · Higher grade (F → D)
- DLafayette Park LakeSt. Louis city County · 12.8 mi · Higher grade (F → D)
- DJefferson LakeSt. Louis city County · 12 mi · Higher grade (F → D)
Nearby Lakes in St. Louis County
Explore Spanish Lake across LakeGrade
Species activity outlook by water temperature and season
Where to stay at Missouri's top lakes, each with its grade
Very high nutrients, dense algae, poor clarity
Missouri's cleanest and most-polluted lakes, ranked
More Missouri Lake Rankings
Other Grade F Lakes in Missouri
Jefferson County · Clarity: 1.3 ft
St. Charles County · Clarity: 2.6 ft
St. Charles County · Clarity: 2.3 ft
St. Francois County · Clarity: 1.1 ft
Audrain County · Clarity: 1.8 ft
Ralls County · Very Poor
Hypereutrophic Lakes in Missouri
More records, surveys & data sources
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth is a modeled estimate.
Regulated Pollution Sources Nearby
5 EPA-permitted facilities operate within about 5 miles of Spanish Lake under Clean Water Act (NPDES) discharge permits, including 1 classified by the EPA as major discharger. 3 facilities have a reported Clean Water Act violation in the past three years.
- Msd Coldwater Creek WwtpFlorissant · 3.4 mi away · NPDES MO0025160MajorRecent violation
- St Louis, Chain Rocks WtpSt. Louis · 3.5 mi away · NPDES MO0000604Recent violation
- Spire Missouri Inc.St. Louis · 4.9 mi away · NPDES MO0114804Recent violation
- Maintenance Bldg City Of Black JackBlack Jack · 3.1 mi away · NPDES MONX00333
- Chain Of Rocks RdfGranite City · 4.8 mi away · NPDES IL0075523
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)
Lake size & watershed from HydroLAKES (HydroSHEDS)
Grading methodology based on Metropolitan Council standards
Public boat-access points from the USGS National Boat Ramps inventory
Most recent sample: 2024-09-21
Monitoring stations: 1