Hillsborough-Flynn Lake
Hillsborough-Flynn Lake in Hillsborough County, Florida has a water quality grade of B (Good). Water clarity: 6 ft visibility. Phosphorus: 10.5 µg/L.
- Clarity
- 6 ft
- Type
- Mesotrophic
- Trend
- ↓ Declining
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Hillsborough-Flynn Lake is a mesotrophic lake in Hillsborough County, Florida. Water quality is graded B based on 1 sampling years through 2025. Overall water quality is declining over recent sampling years. Compared to the 123 other monitored lakes in Hillsborough County, Hillsborough-Flynn Lake ranks #1 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2025-02-26. Grade methodology: LakeQuality methodology.
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Swimming Safety
Grade onlyLow algae
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 6 ft. Phosphorus level: 10.5 µg/L. Trophic State Index: 45.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 6 ft | Not graded |
| Phosphorus | 10.5 µg/L | Good |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 45 | Mesotrophic |
Moderate nutrients, good water quality
Where to stay near Hillsborough-Flynn Lake
Compare lakeside cabins, hotels, and vacation rentals near Hillsborough-Flynn 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 Hillsborough-Flynn Lake
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Fishing Hillsborough-Flynn Lake
Water Quality Trend: ↓ Declining
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.044 m/yr | 5 |
| Phosphorus | ↓ Declining | +1.3 µg/L/yr | 5 |
EPA Impairment Status
Hillsborough-Flynn 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 FL1402C · Official waterbody report · Matched by proximity (0.95 km)
County Ranking
Ranked #1 of 124 lakes in Hillsborough County
Nearby Lakes in Hillsborough County
Frequently asked questions about Hillsborough-Flynn Lake
Where is Hillsborough-Flynn Lake?
- Hillsborough-Flynn Lake is a lake in Hillsborough County, Florida. LakeQuality grades it B for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Hillsborough-Flynn Lake?
- Hillsborough-Flynn Lake in Hillsborough County, Florida has a water quality grade of B (Good). Water clarity: 6 ft visibility. Phosphorus: 10.5 µg/L.
Is Hillsborough-Flynn Lake safe to swim in?
- Good for swimming, clear water with low algae levels. Hillsborough-Flynn Lake has a water quality grade of B (Good). Always check local health department advisories before swimming.
Explore Hillsborough-Flynn Lake across LakeQuality
More Florida Lake Rankings
Other Grade B Lakes in Florida
Mesotrophic Lakes in Florida
Where this data comes from
268 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_WQX268 samples · 2020–2025
Monitoring station identifiers (3)
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