What is the cleanest lake in Rock Island County, Illinois?

Bowles Slough in Rock Island County is the highest-rated lake in Rock Island County, Illinois with an EPA water quality grade of NR.

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 Rock Island County, Illinois

Bowles Slough in Rock Island County leads the rankings with a water quality grade of NR. Below are the top 2 cleanest monitored lakes in Rock Island County, Illinois, ranked by EPA water quality score.

Ranked List

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	Bowles Slough	Rock Island	NR	-	-	-
2	Lake George	Rock Island	NR	-	-	-

Ranked List

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