Hillsborough-Mill Lake
Hillsborough-Mill Lake in Hillsborough County, Florida has a water quality grade of C (Fair). Water clarity: 1.9 ft visibility. Phosphorus: 52 µg/L.
- Clarity
- 1.9 ft
- Type
- Eutrophic
- Trend
- → Stable
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Hillsborough-Mill Lake is a productive, nutrient-rich eutrophic lake in Hillsborough County, Florida. Water quality is graded C based on 1 sampling years through 2020. 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. Grade methodology: LakeQuality methodology.
Watch Hillsborough-Mill Lake water quality
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Swimming Safety
Grade onlyLimited data
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.
Generally safe for swimming, moderate water quality
Water Quality Grade: C (Fair)
Very murky, less than 1.9 ft of visibility. Phosphorus level: 52 µg/L. Trophic State Index: 64.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 1.9 ft | Not graded |
| Phosphorus | 52 µg/L | Fair |
| Chlorophyll-a (Algae) | No recent samples | |
| Trophic State Index (TSI) | 64 | Eutrophic |
High nutrients, frequent algae, reduced clarity
Where to stay near Hillsborough-Mill Lake
Compare lakeside cabins, hotels, and vacation rentals near Hillsborough-Mill 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-Mill Lake
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Fishing Hillsborough-Mill Lake
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.167 m/yr | 5 |
| Phosphorus | ↓ Declining | +1.5 µg/L/yr | 5 |
EPA Impairment Status
Hillsborough-Mill 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 (2.53 km)
County Ranking
Ranked #86 of 124 lakes in Hillsborough County
Nearby Lakes With Higher Grades
Hillsborough-Mill Lake holds Grade C. 2 nearby lakes hold higher nutrient-and-algae grades — useful for a swim day, not a reason to skip lodging here.
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. LakeQuality grades it C for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Hillsborough-Mill Lake?
- Hillsborough-Mill Lake in Hillsborough County, Florida has a water quality grade of C (Fair). Water clarity: 1.9 ft visibility. Phosphorus: 52 µg/L.
Is Hillsborough-Mill Lake safe to swim in?
- Generally safe for swimming, moderate water quality. Hillsborough-Mill Lake has a water quality grade of C (Fair). Always check local health department advisories before swimming.
Explore Hillsborough-Mill Lake across LakeQuality
More Florida Lake Rankings
Other Grade C Lakes in Florida
Eutrophic Lakes in Florida
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)
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