What is the cleanest lake in Illinois?

Lake Calumet in Cook County has the cleanest nutrient and algae readings in Illinois, with 4.1 feet of measured water clarity.

How are these rankings calculated?

Nutrients and algae, total phosphorus, nitrogen, chlorophyll-a and turbidity, are read against EPA National Lakes Assessment 2022 condition classes for that lake’s ecoregion. Water clarity (Secchi depth) is measured and shown separately. Lakes without enough recent samples are listed without a condition class rather than ranked low. Source data comes from the EPA Water Quality Portal.

Cleanest Lakes in Illinois

Lake Calumet in Cook County leads the rankings on measured clarity and nutrients and 4.1 ft of clarity. Below are the top 6 cleanest monitored lakes in Illinois, ranked on EPA nutrient and algae measurements.

Ranked List

#	Lake	County	Clarity	Phosphorus	Algae
1	Lake Calumet	Cook	4.1 ft	16.5 µg/L	5.4 µg/L
2	Kinkaid Lake	Jackson	-	23.5 µg/L	15.8 µg/L
3	Long Lake	Lake	3.4 ft	81 µg/L	57.1 µg/L
4	Salem Lake	Marion	1 ft	234 µg/L	77.5 µg/L
5	Vandalia Lake	Fayette	1.3 ft	103.5 µg/L	84.4 µg/L
6	Fairfield Lake	Wayne	1.3 ft	148 µg/L	35.4 µg/L

Ranked List

More Answers for Illinois