Keystone Lake
Keystone Lake in Hillsborough County, Florida is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 2.6 ft visibility. Phosphorus: 18 µg/L. Surface area: 431 acres.
- Clarity
- 2.6 ft
- Area
- 431 acres
- Trend
- ↓ Declining
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Why Keystone Lake has no grade
We grade a lake only when the monitoring record supports a letter: at least three phosphorus or chlorophyll-a samples in the last ten years, scored against EPA National Lakes Assessment thresholds for this lake’s ecoregion. For Keystone Lake, no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years). Sampling here has recorded water clarity and phosphorus, but not algae (chlorophyll-a).
Not Rated is not an F. It is EPA Integrated Reporting Category 3 — insufficient information. The water here may be excellent or poor; nobody has measured enough of it to say. Everything below that has been measured is still reported on this page.
Sampling is run by FDEP and volunteer programs, and published through the EPA Water Quality Portal. Read the full grading methodology.
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. Grade methodology: LakeQuality methodology.
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Swimming Safety
Not ratedLimited data
Not rated for swimming — there is not enough monitoring data to judge this lake
Water quality measurements for Keystone Lake
These readings exist but are not enough for an A–F grade — see why.
Very murky, less than 2.6 ft of visibility. Phosphorus level: 18 µg/L. Trophic State Index: 55.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 2.6 ft | Not graded |
| Phosphorus | 18 µg/L | Not graded |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 55 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Keystone Lake
Compare lakeside cabins, hotels, and vacation rentals near Keystone Lake in Hillsborough 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 Keystone Lake
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Lake Details
| Characteristic | Value |
|---|---|
| Surface Area | 431 acres |
No bathymetric survey has been published for Keystone Lake, so its depth is not documented here.
Fishing Keystone Lake
Water Quality Trend: ↓ Declining
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↓ Declining | -0.701 m/yr | 6 |
| Phosphorus | ↓ Declining | +0.64 µg/L/yr | 6 |
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)
EPA Impairment Status
Keystone Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).
Causes of impairment
Source: EPA ATTAINS assessment unit FL1474A · Official waterbody report · Matched by proximity (2.37 km)
Graded lakes near Keystone Lake
Keystone Lake has no grade, but these lakes within a short drive do.
Nearby Lakes in Hillsborough County
Frequently asked questions about Keystone Lake
Where is Keystone Lake?
- Keystone Lake is a lake in Hillsborough County, Florida. LakeQuality has not rated this lake (UNRATED) — no nutrient or algae measurement meets the evidence bar (at least 3 samples within 10 years).
What is the water quality grade for Keystone Lake?
- Keystone Lake in Hillsborough County, Florida is not rated for water quality — its monitoring record does not meet the evidence bar. Water clarity: 2.6 ft visibility. Phosphorus: 18 µg/L. Surface area: 431 acres.
Is Keystone Lake safe to swim in?
- Not rated for swimming — there is not enough monitoring data to judge this lake. Keystone Lake is not rated for water quality — its monitoring record does not meet the evidence bar. Always check local health department advisories before swimming.
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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)
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