What is the cleanest lake in Marion County, Iowa?

Roberts Creek Lake in Marion County is the highest-rated lake in Marion County, Iowa with an EPA water quality grade of F and 1.5 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 Marion County, Iowa

Roberts Creek Lake in Marion County leads the rankings with a water quality grade of F and 1.5 ft of clarity. Below are the top 2 cleanest monitored lakes in Marion County, Iowa, ranked by EPA water quality score.

Ranked List

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	Roberts Creek Lake	Marion	F	1.5 ft	115 µg/L	44.6 µg/L
2	Lake Red Rock	Marion	NR	-	-	-

Ranked List

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