What is the cleanest lake in Calhoun County, Iowa?

South Twin Lake in Calhoun County is the highest-rated lake in Calhoun County, Iowa 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 Calhoun County, Iowa

South Twin Lake in Calhoun County leads the rankings with a water quality grade of NR. Below are the top 1 cleanest monitored lakes in Calhoun County, Iowa, ranked by EPA water quality score.

Ranked List

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	South Twin Lake	Calhoun	NR	-	-	-

Ranked List

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