What is the cleanest lake in Cook County, Illinois?

Lake Calumet in Cook County is the highest-rated lake in Cook County, Illinois with an EPA water quality grade of A and 4.1 feet of water clarity.

How are these rankings calculated?

Lakes are graded A through F on nutrients and algae — total phosphorus, nitrogen, chlorophyll-a, and turbidity — against EPA National Lakes Assessment 2022 condition classes for that lake’s ecoregion. Water clarity (Secchi depth) is measured and shown; it is not the letter. Lakes without enough recent samples are UNRATED, not given an F. Source data comes from the EPA Water Quality Portal.

Cleanest Lakes in Cook County, Illinois

Lake Calumet in Cook County leads the rankings with a water quality grade of A and 4.1 ft of clarity. Below are the top 15 cleanest monitored lakes in Cook County, Illinois, ranked by EPA water quality score.

Ranked List

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	Lake Calumet	Cook	A	4.1 ft	16.5 µg/L	5.4 µg/L
2	Big Bend Lake	Cook	NR	-	-	-
3	Beck Lake	Cook	NR	-	-	-
4	Spring Lake	Cook	NR	-	-	-
5	Hawley Lake	Cook	NR	-	-	-
6	Keene Lake	Cook	NR	-	-	-
7	Hawthorn Lake	Cook	NR	-	-	-
8	Baker Lake	Cook	NR	-	-	-
9	Goose Lake	Cook	NR	-	-	-
10	Tampier Slough	Cook	NR	-	-	-
11	Longjohn Slough	Cook	NR	-	-	-
12	Orland Lake	Cook	NR	-	-	-
13	Lake Cottage Grove	Cook	NR	-	-	-
14	Dead Stick Pond	Cook	NR	-	-	-
15	Wolf Lake	Cook	NR	-	-	-

Ranked List

More Answers for Cook County, Illinois