Keystone Lake
Hillsborough County, Florida431 acresView mapDirections
Florida DEP publishes the water-quality measurements for Keystone Lake. Here is what has been measured.
- Limited data
Keystone Lake in Hillsborough County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 2.6 ft visibility. Phosphorus: 18 µg/L. Surface area: 431 acres.
Keystone Lake is a 431-acre lake in Hillsborough County, Florida. Overall water quality is declining over recent sampling years.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-06-10. Methodology: how these readings are compared.
Swimming conditions
No readingLimited data
Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
Whether 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 Keystone Lake
These are the measurements Florida DEP publishes for Keystone Lake, shown as reported. The condition class beside each reading is the EPA National Lakes Assessment class for this lake’s ecoregion.
Very murky, less than 2.6 ft of visibility. Phosphorus 18 µg/L. TSI 55.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 2.6ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 18µg/L | Measured, not scored The nutrient that most limits algae growth in freshwater. More phosphorus, more algae potential. |
| 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. | 55 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
Ask about Keystone Lake
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Lake Details
Surface area
431 acres
No bathymetric survey has been published for Keystone Lake, so its depth is not documented here.
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Fishing Keystone Lake
Water Quality Trend: Worsening
Based on 6 years of monitoring (2020–2025).
Water clarity
Worsening6 years
Phosphorus
Worsening+0.64 µg/L/yr6 years
Reservoir Info (USACE NID)
Keystone Lake is a man-made reservoir impounded by the Keystone Lake Water Conservation Structure, built primarily for flood risk reduction on the Keystone Lake; other-type dam, 6 ft tall and 24.25 ft long.
- Surface area
- 431 ac
- Normal storage
- 510 ac-ft
- Max storage
- 1,851 ac-ft
- Hazard class
- Significant
- Owner
- SWFWMD
All listed purposes: Flood Risk Reduction;Recreation;Water Supply.
Source: USACE National Inventory of Dams, NID ID FL12038 · Operator website · Matched by proximity (0.64 km)
Nearby Lakes in Hillsborough County
Frequently asked questions about Keystone Lake
Where is Keystone Lake?
- 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 Keystone Lake?
- Keystone Lake in Hillsborough County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 2.6 ft visibility. Phosphorus: 18 µg/L. Surface area: 431 acres.
Is Keystone Lake safe to swim in?
- Nutrient and algae readings are not a swimming clearance. Check local advisories before you swim.
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Where this data comes from
6 measurements from 1 monitoring station, 2025. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- Submitting organization not recorded for these samples6 samples · 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.