Lake Markham
Lake Markham in Seminole County, Florida has a water quality grade of B (Good). Water clarity: 5.8 ft visibility. Phosphorus: 8 µg/L.
- Clarity
- 5.8 ft
- Typical in August
- 88°F
- Max depth
- ~36 ft est.
- Type
- Mesotrophic
- Trend
- → Stable
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Lake Markham is a mesotrophic lake in Seminole County, Florida with an estimated average depth of about 36 feet. Water quality is graded B based on 1 sampling years through 2025. Water clarity is declining over recent sampling years. Compared to the 121 other monitored lakes in Seminole County, Lake Markham ranks #26 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-05-13. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyLimited data
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.
Good for swimming, clear water with low algae levels
Water Quality Grade: B (Good)
Murky, only visible to about 5.8 ft. Phosphorus level: 8 µg/L. Trophic State Index: 43.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 5.8 ft | Not graded |
| Phosphorus | 8 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 43 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Lake Markham
Compare lakeside cabins, hotels, and vacation rentals near Lake Markham in Seminole 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 Lake Markham
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Planning a whole trip? See where to stay at Florida’s top lakes →
Water Temperature
Lake Markham typically sits around 88°F at the surface in August. Summer average is about 87°F. Usually warmest in Aug (about 88°F) and coldest in Dec (about 66°F). These are typical values by month — not a live reading.
Typical surface water temperature by month, from 52 field readings (2010–2025) via the EPA Water Quality Portal. See the full Lake Markham water temperature breakdown →
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | ~36 ft est. |
| Average Depth | ~9 ft est. |
Depth marked “est.” is a modeled maximum from GLOBathy (Khazaei et al. 2022, CC0), not a measured survey. Florida has not published bathymetry for Lake Markham.
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.
Fishing Lake Markham
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.61 m/yr | 5 |
| Phosphorus | ↑ Improving | -2.9 µg/L/yr | 5 |
EPA Impairment Status
Lake Markham 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 FL2956A · Official waterbody report · Matched by proximity (0.87 km)
County Ranking
Ranked #26 of 122 lakes in Seminole County
Nearby Lakes in Seminole County
Frequently asked questions about Lake Markham
Where is Lake Markham?
- Lake Markham is a lake in Seminole County, Florida. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Lake Markham?
- Lake Markham in Seminole County, Florida has a water quality grade of B (Good). Water clarity: 5.8 ft visibility. Phosphorus: 8 µg/L.
Is Lake Markham safe to swim in?
- Good for swimming, clear water with low algae levels. Lake Markham has a water quality grade of B (Good). Always check local health department advisories before swimming.
What is the water temperature of Lake Markham?
- Lake Markham typically sits around 88°F at the surface in August, from 52 EPA Water Quality Portal field readings (2010–2025). That is a typical value for the month, not a live reading.
How deep is Lake Markham?
- No published bathymetric survey covers Lake Markham, so its depth has not been measured. The HydroLAKES global model estimates an average depth of about 36 feet, but that is a modelled estimate derived from surrounding terrain rather than a measurement on the water, so treat it as approximate.
Explore Lake Markham across LakeQuality
Planning a trip around Canaveral?
Lake Markham is about 39 miles from Canaveral National Seashore. Crowds there swing hard by season, so the month you pick changes both how busy the park is and what lodging costs.
Best time to visit Canaveral →More Florida Lake Rankings
Other Grade B Lakes in Florida
Mesotrophic Lakes in Florida
Where this data comes from
39 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 samples39 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)