Sylvan Lake
Seminole County, FloridaView mapDirections
Florida DEP publishes the water-quality measurements for Sylvan Lake. Here is what has been measured.
- Mesotrophic
- Impaired · Mercury
- Limited data
Sylvan Lake in Seminole County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 5.6 ft visibility. Phosphorus: 14 µg/L.
Sylvan Lake is a mesotrophic lake in Seminole County, Florida. Water clarity is declining over recent sampling years. Compared to the 121 other monitored lakes in Seminole County, Sylvan Lake ranks #72 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-05-13. Methodology: how these readings are compared.
If you are planning to stay, you can search lake houses and cabins around Sylvan Lake on Vrbo, or look for a hotel room near the lake on Booking.com or Expedia.
Swimming conditions
Readings onlyLimited data
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. Sylvan Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, pH / acidity. Check local advisories before you swim.
Whether Sylvan 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 Sylvan Lake
These are the measurements Florida DEP publishes for Sylvan 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 5.6 ft. Phosphorus 14 µg/L. TSI 47.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 5.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 14µg/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. | 47 | Mesotrophic OligotrophicMesotrophicEutrophicHypereutrophic |
Moderate nutrients, good water quality
Ask about Sylvan Lake
Answers come straight from the public measurements and survey records on this page.
Water Temperature
Sylvan Lake typically sits around 72°F at the surface in November. Summer average is about 87°F. Usually warmest in Jul (about 88°F) and coldest in Feb (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 (88°F).
Typical surface water temperature by month, from 54 field readings (2010–2025) via the EPA Water Quality Portal. See the full Sylvan Lake water temperature breakdown →
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Stays near Sylvan Lake
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Fishing Sylvan Lake
Water Quality Trend: Stable
Based on 5 years of monitoring (2020–2024).
Water clarity
Worsening5 years
Phosphorus
Improving-2.9 µg/L/yr5 years
EPA Impairment Status
Sylvan 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: Aquatic life, Fish consumption.
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit FL2961 · Official waterbody report
Nearby Lakes in Seminole County
Frequently asked questions about Sylvan Lake
Where is Sylvan Lake?
- Sylvan Lake is a lake in Seminole County, Florida. Its water-quality measurements are published by Florida DEP and shown on this page as reported.
What is the water quality of Sylvan Lake?
- Sylvan Lake in Seminole County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 5.6 ft visibility. Phosphorus: 14 µg/L.
Is Sylvan Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Sylvan Lake is listed impaired under Clean Water Act §303(d) (IR 4A) for mercury, pH / acidity. Check local advisories before you swim.
What is the water temperature of Sylvan Lake?
- Sylvan Lake typically sits around 72°F at the surface in November, from 54 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
Explore Sylvan Lake across LakeQuality
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Where this data comes from
40 measurements from 1 monitoring station, 2020–2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Submitting organization not recorded for these samples40 samples · 2020–2025
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