Jefferson Lake
St. Louis city County, MissouriView mapDirections
Not enough samples to grade — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). No letter yet. Here is what we do have.
- Limited data
Jefferson Lake in St. Louis city County, Missouri is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 70 µg/L. Chlorophyll-a (algae): 55.2 µg/L.
- Phosphorus
- 70 µg/L
- Chlorophyll-a
- 55.2 µg/L
- Trend
- ↑ Improving
Stays via Stay22
Stays near Jefferson Lake
Compare lakeside cabins, hotels, and vacation rentals near Jefferson 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.
Top-rated places to stay near Jefferson Lake
Prices for Sep 11–13, 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 →
Watch Jefferson Lake’s letter
Email me if this lake’s grade moves. Grades stay free.
Or email
Why Jefferson Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Jefferson Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded phosphorus and algae (chlorophyll-a), but not water clarity.
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by Missouri DNR and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
Jefferson Lake is a lake in St. Louis city County, Missouri. Overall water quality is improving over recent sampling years.
Source: EPA Water Quality Portal sampling records, Missouri DNR, last sampled 2020-08-24. Grade methodology: LakeQuality methodology.
Swimming Safety
Not ratedLimited data
The letter is not a swimming clearance. Check local advisories before you swim.
Water quality measurements for Jefferson Lake
These readings exist but are not enough for an A–F grade — see why.
No clarity data. Phosphorus 70 µg/L. Chlorophyll-a 55.2 µg/L. TSI 68.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 70 µg/L | Not graded |
| Chlorophyll-a (Algae) | 55.2 µg/L | Not graded |
| Trophic State Index (TSI) | 68 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Fishing Jefferson Lake
Water Quality Trend: ↑ Improving
Based on 2 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Phosphorus | → Stable | -0.3 µg/L/yr | 2 |
| Chlorophyll-a | ↑ Improving | -7.97 µg/L/yr | 2 |
Regulated Pollution Sources Nearby
1 EPA-permitted facility operate within about 5 miles of Jefferson Lake under Clean Water Act (NPDES) discharge permits.
- Solae LlcSt. Louis · 0.9 mi away · NPDES MONX00102
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.
Graded lakes near Jefferson Lake
Jefferson Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in St. Louis city County
Frequently asked questions about Jefferson Lake
Where is Jefferson Lake?
- Jefferson Lake is a lake in St. Louis city County, Missouri. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Jefferson Lake?
- Jefferson Lake in St. Louis city County, Missouri is not rated for water quality — its monitoring record does not meet the evidence bar. Phosphorus: 70 µg/L. Chlorophyll-a (algae): 55.2 µg/L.
Is Jefferson Lake safe to swim in?
- The letter is not a swimming clearance. Check local advisories before you swim.
Explore Jefferson Lake across LakeQuality
Planning a trip around Gateway Arch?
Jefferson Lake is about 4 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
Other Lakes in Missouri
Eutrophic Lakes in Missouri
Where this data comes from
2 measurements from 1 monitoring station, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Missouri Dept. of Natural Resources
MDNR2 samples · 2020
Analytical methods
- Nitrogen and Phosphorus, Total, Whole-water, Alkaline Persulfate Digest
- 445.0 ~ EPA; Chlorophyll and Pheophytin in Algae by Fluorescence
Monitoring station identifiers (1)
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
Regulated discharger data from EPA ECHO (ICIS-NPDES)