What is the cleanest lake in Fond du Lac County, Wisconsin?

Long Lake in Fond du Lac County is the highest-rated lake in Fond du Lac County, Wisconsin with an EPA water quality grade of B and 9.1 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 Fond du Lac County, Wisconsin

Long Lake in Fond du Lac County leads the rankings with a water quality grade of B and 9.1 ft of clarity. Below are the top 9 cleanest monitored lakes in Fond du Lac County, Wisconsin, ranked by EPA water quality score.

Ranked List

#	Lake	County	Grade	Clarity	Phosphorus	Algae
1	Long Lake	Fond du Lac	B	9.1 ft	19.3 µg/L	-
2	Forest Lake	Fond du Lac	B	14 ft	14.1 µg/L	-
3	Auburn Lake	Fond du Lac	B	7.6 ft	24.4 µg/L	-
4	Kettle Moraine Lake	Fond du Lac	B	11 ft	16.2 µg/L	-
5	De Neveu Lake	Fond du Lac	B	11 ft	18.1 µg/L	-
6	Mullet Lake	Fond du Lac	NR	-	-	-
7	Spruce Lake	Fond du Lac	NR	-	-	-
8	Birchwood Lake	Fond du Lac	NR	-	-	-
9	Mud Lake	Fond du Lac	NR	-	-	-

Ranked List

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