Joanna Lake
Lake County, FloridaView mapDirections
Florida DEP publishes the water-quality measurements for Joanna Lake. Here is what has been measured.
- Impaired · Mercury
- Limited data
Joanna Lake in Lake County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 4.8 ft visibility. Phosphorus: 29 µg/L.
Joanna Lake is a lake in Lake County, Florida. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2023-05-23. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Joanna Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Joanna Lake is safe to swim in today is a call for the Florida Department of Environmental Protection and the county health department, who post current advisories. LakeQuality does not issue swimming clearances.
Water quality measurements for Joanna Lake
These are the measurements Florida DEP publishes for Joanna Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Murky, only visible to about 4.8 ft. Phosphorus 29 µg/L. TSI 54.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 4.8ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 29µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| 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. | 54 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
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Fishing Joanna Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+1.77 µg/L/yr6 years
EPA Impairment Status
Joanna Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4A).
Causes of impairment
Designated uses not supporting: Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit FL2821B · Official waterbody report
Nearby Lakes in Lake County
Frequently asked questions about Joanna Lake
Where is Joanna Lake?
- Joanna Lake is a lake in Lake County, Florida. Its water-quality measurements are published by Florida DEP and shown on this page as reported.
What is the water quality of Joanna Lake?
- Joanna Lake in Lake County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 4.8 ft visibility. Phosphorus: 29 µg/L.
Is Joanna Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Joanna Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
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Where this data comes from
8 measurements from 1 monitoring station, 2020–2023. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Submitting organization not recorded for these samples8 samples · 2020–2023
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