What is the cleanest lake in Clay County, Iowa?

Stolley Pit Lake in Clay County is the highest-rated lake in Clay County, Iowa with an EPA water quality grade of C and 2.7 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 Clay County, Iowa

Stolley Pit Lake in Clay County leads the rankings with a water quality grade of C and 2.7 ft of clarity. Below are the top 6 cleanest monitored lakes in Clay County, Iowa, ranked by EPA water quality score.

Ranked List

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	Stolley Pit Lake	Clay	C	2.7 ft	48 µg/L	17.3 µg/L
2	Elk Lake	Clay	NR	-	-	-
3	Dan Green Slough	Clay	NR	-	-	-
4	Trumbull Lake	Clay	NR	-	-	-
5	Mud Lake	Clay	NR	-	-	-
6	Round Lake	Clay	NR	-	-	-

Ranked List

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