Lake St. John
Concordia Parish County, LouisianaView mapDirections
LDEQ publishes the water-quality measurements for Lake St. John. Here is what has been measured.
- Eutrophic
- Impaired · Pathogens (E. coli, fecal)
- Public access
- Limited data
Lake St. John in Concordia Parish County, Louisiana has water-quality measurements published by LDEQ, shown here as reported. Phosphorus: 50 µg/L.
Lake St. John is a productive, nutrient-rich eutrophic lake in Concordia Parish County, Louisiana. Limited fish-species data available. Public access is available. Compared to the 2 other monitored lakes in Concordia Parish County, Lake St. John ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, your state environmental agency, last sampled 2023-10-03. Methodology: how these readings are compared.
Swimming conditions
Readings onlyBacteria advisory
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. Lake St. John is listed impaired under Clean Water Act §303(d) (IR 5) for pathogens (E. coli, fecal), pH / acidity, temperature. Check local advisories before you swim.
Whether Lake St. John is safe to swim in today is a call for the Louisiana Department of Environmental Quality and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Lake St. John
These are the measurements LDEQ publishes for Lake St. John, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
No clarity data. Phosphorus 50 µg/L. TSI 61.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | No reading How deep a black-and-white disk stays visible from the surface. Higher is clearer. | |
| Total phosphorus | 50µg/L | Fair GoodFairPoor |
| Chlorophyll-a (algae) | No reading The green pigment in algae — a direct measure of how much algae is in the water. | |
| Trophic state (TSI)Carlson's 0–100 index of how much algae a lake can support, from clarity, phosphorus and chlorophyll-a. | 61 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Lake St. John
Answers come straight from the public measurements and survey records on this page.
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Fishing Lake St. John
EPA Impairment Status
Lake St. John is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).
Causes of impairment
Designated uses not supporting: Aquatic life, Recreation.
Source: EPA ATTAINS assessment unit LA101603_00 · Official waterbody report
Nearby Lakes in Concordia Parish County
Frequently asked questions about Lake St. John
Where is Lake St. John?
- Lake St. John is a lake in Concordia Parish County, Louisiana. Its water-quality measurements are published by LDEQ and shown on this page as reported.
What is the water quality of Lake St. John?
- Lake St. John in Concordia Parish County, Louisiana has water-quality measurements published by LDEQ, shown here as reported. Phosphorus: 50 µg/L.
Is Lake St. John safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake St. John is listed impaired under Clean Water Act §303(d) (IR 5) for pathogens (E. coli, fecal), pH / acidity, temperature. Check local advisories before you swim.
Can I fish at Lake St. John?
- Public access to Lake St. John is listed as yes on the lake record. Seasons, size and bag limits, and whether you need a license are set by Louisiana's fish and wildlife agency, so check its current regulations before you go.
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Where this data comes from
20 measurements from 1 monitoring station, 2022–2023. Retrieved from the EPA Water Quality Portal on 2026-08-21.
Collected and reported by
- LDEQ/Water Planning and Assessment (Louisiana)
LADEQWPD_WQX20 samples · 2022–2023
Analytical methods
- Total Phosphorus After Block Digestion
- 2130 B ~ Nephelometric Method
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
Impairment status from EPA ATTAINS 303(d) database