Lake St. John
Lake St. John in Concordia Parish County, Louisiana has a water quality grade of C (Fair). Phosphorus: 50 µg/L.
- Type
- Eutrophic
- Public access
- Yes
Lake St. John is a productive, nutrient-rich eutrophic lake in Concordia Parish County, Louisiana. Water quality is graded C based on 1 sampling years through 2023. Limited fish-species data available. Public access is available with 1 public boat landing. 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. Grade methodology: LakeGrade methodology.
Watch Lake St. John water quality
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Swimming Safety
Grade onlyBacteria advisory
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
No clarity data. Phosphorus level: 50 µg/L. Trophic State Index: 61.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | No recent samples | |
| Phosphorus | 50 µg/L | Fair |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 61 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Lake St. John
Compare lakeside cabins, hotels, and vacation rentals near Lake St. John in Concordia Parish County, Louisiana — 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 Lake St. John
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Recreation & Access
- Old LDWF District 4 Office RampPublic
Named access points from the USGS National Boat Ramps inventory, snapped within 5 km. More lakes with boat ramps
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
Source: EPA ATTAINS assessment unit LA101603_00 · Official waterbody report
County Ranking
Ranked #1 of 3 lakes in Concordia Parish County
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. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake St. John?
- Lake St. John in Concordia Parish County, Louisiana has a water quality grade of C (Fair). Phosphorus: 50 µg/L.
Is Lake St. John safe to swim in?
- Generally safe for swimming, moderate water quality. Lake St. John has a water quality grade of C (Fair). Always check local health department advisories before swimming.
Are there boat ramps on Lake St. John?
- Lake St. John has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include Old LDWF District 4 Office Ramp. Public access is listed as yes.
Explore Lake St. John across LakeGrade
More Louisiana Lake Rankings
Other Grade C Lakes in Louisiana
Catahoula Parish County · Fair
LaSalle Parish County · Fair
Rapides Parish County · Fair
Rapides Parish County · Fair
Jackson Parish County · Fair
Rapides Parish County · Fair
Eutrophic Lakes in Louisiana
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)
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
Named boat-access points from the USGS National Boat Ramps inventory