What is the cleanest lake in Mahaska County, Iowa?

Hawthorn Lake in Mahaska County is the highest-rated lake in Mahaska County, Iowa with an EPA water quality grade of D and 2.4 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 Mahaska County, Iowa

Hawthorn Lake in Mahaska County leads the rankings with a water quality grade of D and 2.4 ft of clarity. Below are the top 2 cleanest monitored lakes in Mahaska County, Iowa, ranked by EPA water quality score.

Ranked List

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	Hawthorn Lake	Mahaska	D	2.4 ft	60 µg/L	27.5 µg/L
2	White Oak Lake	Mahaska	F	1.4 ft	125.5 µg/L	68.7 µg/L

Ranked List

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