Isleworth Lake
Isleworth Lake in Orange County, Florida has a water quality grade of B (Good). Water clarity: 9.8 ft visibility. Phosphorus: 6 µg/L.
- Clarity
- 9.8 ft
- Typical in August
- 87°F
- Max depth
- ~33 ft est.
- Type
- Oligotrophic
- Trend
- ↓ Declining
- Public access
- Yes
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Isleworth Lake is a cold, clear oligotrophic lake in Orange County, Florida with an estimated average depth of about 33 feet. Water quality is graded B based on 1 sampling years through 2025. Overall water quality is declining over recent sampling years. Limited fish-species data available. Public access is available with 1 public boat landing. Compared to the 319 other monitored lakes in Orange County, Isleworth Lake ranks #202 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-01-30. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyBacteria A
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.
Based on E. coli testing, Isleworth Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 30 samples across 8 seasons.
This is a historical summary of past testing, not a current condition — bacteria levels change quickly, especially after rain. Always check Florida’s current beach and health-department advisories before swimming.
Water Quality Grade: B (Good)
Moderate clarity, visible to about 9.8 ft. Phosphorus level: 6 µg/L. Trophic State Index: 37.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 9.8 ft | Not graded |
| Phosphorus | 6 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 37 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Where to stay near Isleworth Lake
Compare lakeside cabins, hotels, and vacation rentals near Isleworth Lake in Orange 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.
Top-rated places to stay near Isleworth Lake
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Water Temperature
Isleworth Lake typically sits around 87°F at the surface in August. Summer average is about 88°F. Usually warmest in Jul (about 88°F) and coldest in Jan (about 63°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 64 field readings (2010–2025) via the EPA Water Quality Portal. See the full Isleworth Lake water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~33 ft est. |
| Average Depth | ~6 ft est. |
| Public Access | Yes |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Florida has not published bathymetry for Isleworth Lake.
Lake Size & Watershed
Size, shoreline, and watershed area from HydroLAKES (HydroSHEDS). Mean depth here is modelled, not surveyed — HydroLAKES v1.0 estimates lake depth from surrounding terrain rather than from soundings. Treat it as an approximation, and prefer a state bathymetric survey where one exists.
Recreation & Access
- R. D. Keene Public Boat RampPublic
Named access points in the USGS National Boat Ramps inventory, within about 3 miles. More lakes with boat ramps
Fishing Isleworth Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.115 m/yr | 5 |
| Phosphorus | ↓ Declining | +1.8 µg/L/yr | 5 |
EPA Impairment Status
Isleworth Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 4A).
Causes of impairment
A Total Maximum Daily Load (TMDL) plan has been approved.
Source: EPA ATTAINS assessment unit FL3170W · Official waterbody report · Matched by proximity (0.99 km)
County Ranking
Ranked #202 of 320 lakes in Orange County
Nearby Lakes in Orange County
Frequently asked questions about Isleworth Lake
Where is Isleworth Lake?
- Isleworth Lake is a lake in Orange County, Florida. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Isleworth Lake?
- Isleworth Lake in Orange County, Florida has a water quality grade of B (Good). Water clarity: 9.8 ft visibility. Phosphorus: 6 µg/L.
Is Isleworth Lake safe to swim in?
- Based on E. coli testing, Isleworth Lake never exceeded the EPA safe-swimming threshold (235 MPN/100mL) — on 0% of 30 samples across 8 seasons. That works out to a bacteria swim-safety grade of A — a historical summary of past testing, not a current reading. Isleworth Lake has a water quality grade of B (Good). Bacteria levels can spike quickly after heavy rain, so always check Florida's current beach and health-department advisories before you swim.
What is the water temperature of Isleworth Lake?
- Isleworth Lake typically sits around 87°F at the surface in August, from 64 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Isleworth Lake?
- No published bathymetric survey covers Isleworth Lake, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 33 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Are there boat ramps on Isleworth Lake?
- Isleworth Lake has 1 documented boat landing in the USGS National Boat Ramps inventory. Named access points include R. D. Keene Public Boat Ramp. Public access is listed as yes.
Explore Isleworth Lake across LakeQuality
More Florida Lake Rankings
Other Grade B Lakes in Florida
Oligotrophic Lakes in Florida
Where this data comes from
63 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 samples63 samples · 2020–2025
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
Lake size & watershed from HydroLAKES (HydroSHEDS)
Named boat-access points from the USGS National Boat Ramps inventory