Lake-Joanna
Lake County, FloridaView mapDirections
Florida DEP publishes the water-quality measurements for Lake-Joanna. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
Lake-Joanna in Lake County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 7.5 ft visibility. Phosphorus: 9 µg/L.
Lake-Joanna is a mesotrophic lake in Lake County, Florida. Overall water quality is declining over recent sampling years. Compared to the 127 other monitored lakes in Lake County, Lake-Joanna ranks #3 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-03-19. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLow algae
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-Joanna is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
Whether Lake-Joanna 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 Lake-Joanna
These are the measurements Florida DEP publishes for Lake-Joanna, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Moderate clarity, visible to about 7.5 ft. Phosphorus 9 µg/L. TSI 42.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 7.5ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 9µg/L | Good 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. | 42 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Lake-Joanna
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Lake-Joanna typically sits around 81°F at the surface in October. Summer average is about 84°F. Usually warmest in Aug (about 84°F) and coldest in Mar (about 69°F). These are typical values by month — not a live reading.
Column height runs from this lake’s coldest month (69°F) to its warmest (84°F).
Typical surface water temperature by month, from 10 field readings (2015–2019) via the EPA Water Quality Portal. See the full Lake-Joanna water temperature breakdown →
Stays via Stay22
Stays near Lake-Joanna
Compare lakeside cabins, hotels, and vacation rentals near Lake-Joanna in Lake County, Florida — 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.
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Fishing Lake-Joanna
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+1.73 µg/L/yr6 years
EPA Impairment Status
Lake-Joanna 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 Lake-Joanna
Where is Lake-Joanna?
- Lake-Joanna 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 Lake-Joanna?
- Lake-Joanna in Lake County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 7.5 ft visibility. Phosphorus: 9 µg/L.
Is Lake-Joanna safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Lake-Joanna is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury. Check local advisories before you swim.
What is the water temperature of Lake-Joanna?
- Lake-Joanna typically sits around 81°F at the surface in October, from 10 EPA Water Quality Portal field readings (2015–2019). That is a typical value for the month, not a live reading.
Explore Lake-Joanna across LakeQuality
More lakes in Florida
Other Lakes in Florida
Mesotrophic Lakes in Florida
Where this data comes from
330 measurements from 3 monitoring stations, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- FLORIDA LAKEWATCH
21FLKWAT_WQX330 samples · 2020–2025
Monitoring station identifiers (3)
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