Hillsborough-Mill Lake
Hillsborough County, FloridaView mapDirections
Florida DEP publishes the water-quality measurements for Hillsborough-Mill Lake. Here is what has been measured.
- Eutrophic
- Limited data
Hillsborough-Mill Lake in Hillsborough County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 1.9 ft visibility. Phosphorus: 52 µg/L.
Hillsborough-Mill Lake is a productive, nutrient-rich eutrophic lake in Hillsborough County, Florida. Water clarity is improving over recent sampling years. Compared to the 123 other monitored lakes in Hillsborough County, Hillsborough-Mill Lake ranks #86 for water quality.
Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2020-12-12. Methodology: how these readings are compared.
Swimming conditions
Readings onlyLimited data
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-Mill 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-Mill Lake
These are the measurements Florida DEP publishes for Hillsborough-Mill 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 1.9 ft of visibility. Phosphorus 52 µg/L. TSI 64.
| Measure | Reading | Where it sits |
|---|---|---|
| Water clarity (Secchi depth) | 1.9ft | Measured, not scored How deep a black-and-white disk stays visible from the surface. Higher is clearer. |
| Total phosphorus | 52µg/L | Fair 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. | 64 | Eutrophic OligotrophicMesotrophicEutrophicHypereutrophic |
High nutrients, frequent algae, reduced clarity
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Fishing Hillsborough-Mill Lake
Water Quality Trend: Stable
Based on 5 years of monitoring (2020–2024).
Water clarity
Improving5 years
Phosphorus
Worsening+1.5 µg/L/yr5 years
Nearby Lakes in Hillsborough County
Frequently asked questions about Hillsborough-Mill Lake
Where is Hillsborough-Mill Lake?
- Hillsborough-Mill 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-Mill Lake?
- Hillsborough-Mill Lake in Hillsborough County, Florida has water-quality measurements published by Florida DEP, shown here as reported. Water clarity: 1.9 ft visibility. Phosphorus: 52 µg/L.
Is Hillsborough-Mill 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
48 measurements from 3 monitoring stations, 2020. Retrieved from the EPA Water Quality Portal on 2026-08-02.
Collected and reported by
- FLORIDA LAKEWATCH
21FLKWAT_WQX48 samples · 2020
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.