What is the water quality grade for Carlyle Lake?

Carlyle Lake in Clinton County, Wisconsin received a water quality grade of F (Very Poor). Water clarity: 1.8 ft visibility. Phosphorus: 200.5 µg/L. Surface area: 24580 acres.

Is Carlyle Lake safe to swim in?

Avoid swimming, very poor water quality, potential algae toxins. Carlyle Lake has an overall water quality grade of F. Always check local health department advisories before swimming.

Carlyle Lake

Clinton County, WisconsinHypereutrophic

Carlyle Lake is a 24,580-acre highly nutrient-loaded hypereutrophic lake in Clinton County, IL. Water quality is graded F based on 2 sampling years through 2021.

Source: EPA Water Quality Portal sampling records, local state DNR records, last sampled 2021-11-03. Grade methodology: LakeGrade methodology.

Swimming Safety

Avoid swimming, very poor water quality, potential algae toxins

Water Quality Grade: F, Very Poor

Very murky, less than 1.8 ft of visibility. Phosphorus level: 200.5 µg/L. Trophic State Index: 75.

Metric	Value	Grade
Water Clarity (Secchi Depth)	1.8 ft	F
Phosphorus	200.5 µg/L	F
Chlorophyll-a (Algae)	No data
Trophic State Index (TSI)	75	Hypereutrophic

Very high nutrients, dense algae, poor clarity

Lake Details

Characteristic	Value
Surface Area	24.6K acres

Location

Loading map…

County Ranking

Ranked #1 of 1 lakes in Clinton County

Cleaner Lakes Within 30 Miles

Carlyle Lake holds Grade F. 2 nearby lakes hold higher grades.

See full comparison →

Nearby Lakes in Clinton County

More Wisconsin Lake Rankings

Cleanest lakes in Wisconsin

Top 25 by overall water quality score

Best swimming lakes in Wisconsin

Grade A/B + low algae filter

Family fishing lakes in Wisconsin

Panfish-rich, public access

All Wisconsin lakes

Full state directory

Other Grade F Lakes in Wisconsin

Lake Charlemagne

Cook County · Clarity: 2 ft

Bode Lake North

Cook County · Clarity: 1.5 ft

Great Lakes Quarries West

Cook County · Clarity: 2.5 ft

Bull Frog Lake

Cook County · Clarity: 3 ft

Belly Deep Slough Lake

Cook County · Clarity: 0.7 ft

Sauk Lake

Cook County · Clarity: 1 ft

Hypereutrophic Lakes in Wisconsin

Bode Lake North Belly Deep Slough Lake Sauk Lake Washington Park Lagoon Lake

Reservoir Info (USACE NID)

Carlyle Lake is a man-made reservoir impounded by the Carlyle Dam - Keyesport Levee (completed 1966), built primarily for flood risk reduction on the KASKASKIA RIVER; earth-type dam, 23 ft tall and 9,945 ft long.

Surface area: 24,580 ac
Normal storage: 233,000 ac-ft
Max storage: 1,286,900 ac-ft
Drainage area: 0.9 sq mi
Hazard class: High
Owner: USACE - St. Louis District

All listed purposes: Flood Risk Reduction;Other;Navigation;Fish and Wildlife Pond;Recreation;Water Supply.

Source: USACE National Inventory of Dams, NID ID IL00113 · Operator website

EPA Impairment Status

Carlyle Lake is officially listed as impaired under Clean Water Act §303(d) in the 2024 EPA reporting cycle (IR category 5).

Causes of impairment

MercuryNutrients (phosphorus, nitrogen)

A Total Maximum Daily Load (TMDL) plan has been approved.

Source: EPA ATTAINS assessment unit IL_ROA · Official waterbody report

Data Sources

Water quality data from the EPA Water Quality Portal

Impairment status from EPA ATTAINS 303(d) database

Grading methodology based on Metropolitan Council standards

Most recent sample: 2021-11-03

Monitoring stations: 5