Where is Pinellas-Alligator Lake?

Pinellas-Alligator Lake is a lake in Pinellas County, Florida. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.

Is Pinellas-Alligator Lake safe to swim in?

Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Pinellas-Alligator Lake has a water quality grade of D (Nutrient-rich). Always check local health department advisories before swimming.

What is the water temperature of Pinellas-Alligator Lake?

Pinellas-Alligator Lake typically sits around 86°F at the surface in August, from 75 EPA Water Quality Portal field readings (2010–2012). That is a typical value for the month, not a live reading.

Pinellas-Alligator Lake

Grade D — Nutrient-rich

Nutrient-rich · #27 of 34 lakes in the county · 2.2 ft clear · Hypereutrophic · 79 acres · ↑ from F

Limited DataHypereutrophic

Pinellas-Alligator Lake in Pinellas County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 2.2 ft visibility. Phosphorus: 158.5 µg/L. Surface area: 79 acres.

Clarity: 2.2 ft
Typical in August: 86°F
Area: 79 acres
Type: Hypereutrophic
Trend: ↓ Declining

Grade D measures nutrients and algae, not whether this is a good place for a cabin trip. Cabins and rentals near Pinellas-Alligator Lake →

Find a place to stay →Safe to swim?

Next lake in Pinellas County

DPinellas-Cliff Stephens Park Lake4.5 ft clear · Pinellas CountyView →

PrevLake Chautauqua Where to stay NextPinellas-Cliff Stephens Park Lake

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Pinellas-Alligator Lake is a 79-acre highly nutrient-loaded hypereutrophic lake in Pinellas County, Florida. Water quality is graded D based on 1 sampling years through 2023. Overall water quality is declining over recent sampling years. Compared to the 33 other monitored lakes in Pinellas County, Pinellas-Alligator Lake ranks #27 for water quality.

Source: EPA Water Quality Portal sampling records, FDEP, last sampled 2023-04-01. Grade methodology: LakeQuality methodology.

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Swimming Safety

Grade only

Limited 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.

Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum

Get alerts for Pinellas-Alligator Lake →

Water Quality Grade: D (Nutrient-rich)

Very murky, less than 2.2 ft of visibility. Phosphorus level: 158.5 µg/L. Trophic State Index: 71.

Metric	Value	Grade
Water Clarity (Secchi Depth)	2.2 ft	Not graded
Phosphorus	158.5 µg/L	Poor
Chlorophyll-a (Algae)	No recent samples
Trophic State Index (TSI)	71	Hypereutrophic

Very high nutrients, dense algae, poor clarity

Where to stay near Pinellas-Alligator Lake

Compare lakeside cabins, hotels, and vacation rentals near Pinellas-Alligator Lake in Pinellas 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. The water-quality grade measures nutrients and algae, not lodging — cabins and rentals around Pinellas-Alligator Lake are listed below.

Top-rated places to stay near Pinellas-Alligator Lake

Availability and prices from Stay22 partners (Booking.com, Vrbo, Expedia). We may earn a commission from bookings, at no extra cost to you.

Planning a whole trip? See where to stay at Florida’s top lakes →

Water Temperature

Pinellas-Alligator Lake typically sits around 86°F at the surface in August. Summer average is about 86°F. Usually warmest in Aug (about 86°F) and coldest in Dec (about 56°F). These are typical values by month — not a live reading.

Jan

—

Feb

61°

Mar

—

Apr

—

May

—

Jun

—

Jul

—

Aug

86°

Sep

84°

Oct

—

Nov

—

Dec

56°

Typical surface water temperature by month, from 75 field readings (2010–2012) via the EPA Water Quality Portal.

Lake Details

Characteristic	Value
Surface Area	79 acres

No bathymetric survey has been published for Pinellas-Alligator Lake, so its depth is not documented here.

Fishing Pinellas-Alligator Lake

→ Pinellas-Alligator Lake fishing regulations (limits, seasons, special rules)

Water Quality Trend: ↓ Declining

Based on 5 years of monitoring data (2020-2025).

Metric	Trend	Change/Year	Years
Water Clarity	↓ Declining	-0.059 m/yr	5
Phosphorus	↓ Declining	+12.5 µg/L/yr	5

See year-by-year chart →

Reservoir Info (USACE NID)

Pinellas-Alligator Lake is a man-made reservoir impounded by the Alligator Lake Weir, built primarily for flood risk reduction on the Alligator Creek; earth-type dam, 9 ft tall and 103 ft long.

Surface area: 79 ac
Normal storage: 200 ac-ft
Max storage: 311 ac-ft
Drainage area: 8 sq mi
Hazard class: Significant
Owner: PINELLAS COUNTY

All listed purposes: Flood Risk Reduction;Recreation;Water Supply.

Source: USACE National Inventory of Dams, NID ID FL78002 · Operator website · Matched by proximity (0.34 km)

EPA Impairment Status

Pinellas-Alligator Lake is officially listed as impaired under Clean Water Act §303(d) in the 2022 EPA reporting cycle (IR category 5).

Causes of impairment

Impaired biota (cause unknown)Nutrients (phosphorus, nitrogen)

Source: EPA ATTAINS assessment unit FL1574A · Official waterbody report · Matched by proximity (0.12 km)

County Ranking

Ranked #27 of 34 lakes in Pinellas County

Nearby Lakes With Higher Grades

Pinellas-Alligator Lake holds Grade D. One nearby lake has a higher nutrient-and-algae grade — useful for a swim day, not a reason to skip lodging here.

BLake Chautauqua· 2.1 mi

Nearby Lakes in Pinellas County

NRAlligator LakeView →DAlligator Lake2.6 ft clear · HypereutrophicView →DAlligator Creek LakeHypereutrophicView →DPinellas-Cliff Stephens Park Lake4.5 ft clear · EutrophicView →BLake Chautauqua4.3 ft clear · MesotrophicView →NRChatauqref Lake8.2 ft clearView →

Frequently asked questions about Pinellas-Alligator Lake

Where is Pinellas-Alligator Lake?: Pinellas-Alligator Lake is a lake in Pinellas County, Florida. LakeQuality grades it D for nutrients and algae. The letter is not a swimming clearance.
What is the water quality grade for Pinellas-Alligator Lake?: Pinellas-Alligator Lake in Pinellas County, Florida has a water quality grade of D (Nutrient-rich). Water clarity: 2.2 ft visibility. Phosphorus: 158.5 µg/L. Surface area: 79 acres.
Is Pinellas-Alligator Lake safe to swim in?: Nutrients and algae run higher than average — check local advisories before swimming, and skip the water if you see scum. Pinellas-Alligator Lake has a water quality grade of D (Nutrient-rich). Always check local health department advisories before swimming.
What is the water temperature of Pinellas-Alligator Lake?: Pinellas-Alligator Lake typically sits around 86°F at the surface in August, from 75 EPA Water Quality Portal field readings (2010–2012). That is a typical value for the month, not a live reading.

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