Hillsborough-Keystone Lake
Hillsborough County, FloridaView mapDirections
Florida DEP publishes the water-quality measurements for Hillsborough-Keystone Lake. Here is what has been measured.
- Mesotrophic
Hillsborough-Keystone Lake in Hillsborough County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 6 ft visibility. Phosphorus: 14 µg/L.
Hillsborough-Keystone Lake is a mesotrophic lake in Hillsborough County, Florida. Overall water quality is declining over recent sampling years. Compared to the 123 other monitored lakes in Hillsborough County, Hillsborough-Keystone Lake ranks #18 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-04-06. Methodology: how these readings are compared.
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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. Check local advisories before you swim.
Whether Hillsborough-Keystone 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 Hillsborough-Keystone Lake
These are the measurements Florida DEP publishes for Hillsborough-Keystone 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 6 ft. Phosphorus 14 µg/L. TSI 47.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 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
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Fishing Hillsborough-Keystone Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Stable+0.11 µg/L/yr6 years
Nearby Lakes in Hillsborough County
Frequently asked questions about Hillsborough-Keystone Lake
Where is Hillsborough-Keystone Lake?
- Hillsborough-Keystone Lake is a lake in Hillsborough County, Florida. Its water-quality measurements are published by Florida DEP and shown on this page as reported.
What is the water quality of Hillsborough-Keystone Lake?
- Hillsborough-Keystone Lake in Hillsborough County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 6 ft visibility. Phosphorus: 14 µg/L.
Is Hillsborough-Keystone Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Explore Hillsborough-Keystone Lake across LakeQuality
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Other Lakes in Florida
Mesotrophic Lakes in Florida
Where this data comes from
283 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_WQX283 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.