What is the cleanest lake in Wisconsin?

Green Lake in Green Lake County has the cleanest nutrient and algae readings in Wisconsin, with 13.5 feet of measured water clarity.

How are these rankings calculated?

Nutrients and algae, total phosphorus, nitrogen, chlorophyll-a and turbidity, are read against EPA National Lakes Assessment 2022 condition classes for that lake’s ecoregion. Water clarity (Secchi depth) is measured and shown separately. Lakes without enough recent samples are listed without a condition class rather than ranked low. Source data comes from the EPA Water Quality Portal.

Cleanest Lakes in Wisconsin

Green Lake in Green Lake County leads the rankings on measured clarity and nutrients and 13.5 ft of clarity. Below are the top 50 cleanest monitored lakes in Wisconsin, ranked on EPA nutrient and algae measurements.

Ranked List

#	Lake	County	Clarity	Phosphorus	Algae
1	Green Lake	Green Lake	13.5 ft	38.1 µg/L	4.4 µg/L
2	Lake Beulah	Walworth	10 ft	13.4 µg/L	2.5 µg/L
3	Geneva Lake	Walworth	21 ft	13 µg/L	2.1 µg/L
4	Powers Lake	Kenosha	10 ft	17.2 µg/L	3.4 µg/L
5	Lac Courte Oreilles Lake	Sawyer	12.2 ft	15 µg/L	1.7 µg/L
6	Whitefish Lake	Sawyer	13.5 ft	14 µg/L	1.6 µg/L
7	Round Lake	Sawyer	21.1 ft	14 µg/L	0.9 µg/L
8	Indian Lake	Sawyer	6.5 ft	22.5 µg/L	3.6 µg/L
9	Big Lake	Shawano	8 ft	15 µg/L	2.7 µg/L
10	Christner Lake	Sawyer	12 ft	18.5 µg/L	2.1 µg/L
11	Sand Lake	Barron	13 ft	20 µg/L	1.9 µg/L
12	Sand Lake	Sawyer	10 ft	23.8 µg/L	4.1 µg/L
13	Ashegon Lake	Sawyer	10.5 ft	18 µg/L	2.7 µg/L
14	Blueberry Lake	Sawyer	14.8 ft	17 µg/L	1.6 µg/L
15	Koonz Lake	Shawano	10.8 ft	17 µg/L	1.7 µg/L
16	Little Round Lake	Sawyer	17.3 ft	12 µg/L	1 µg/L
17	Osprey Lake	Sawyer	16 ft	14.9 µg/L	1.4 µg/L
18	Grindstone Lake	Sawyer	17.4 ft	15 µg/L	1.4 µg/L
19	Lost Lake	Sawyer	10.6 ft	19.5 µg/L	1.6 µg/L
20	Gaslyn Lake	Burnett	4.5 ft	31.5 µg/L	4.2 µg/L
21	Durphee Lake	Sawyer	8.1 ft	22 µg/L	3.1 µg/L
22	Malone Lake	Shawano	13.5 ft	18 µg/L	2.1 µg/L
23	Sams Lake	Shawano	11 ft	18 µg/L	2.2 µg/L
24	Oneida Lake	Outagamie	-	15 µg/L	1.4 µg/L
25	Mission Lake	Shawano	17.5 ft	17 µg/L	2.1 µg/L
26	Bealeau Lake	Shawano	11.5 ft	17 µg/L	2.2 µg/L
27	King Lake	Marinette	-	9 µg/L	0.8 µg/L
28	Mole Lake	Forest	8.5 ft	15.6 µg/L	1.3 µg/L
29	Bug Lake	Forest	-	9.5 µg/L	1 µg/L
30	Cloud Lake	Forest	-	13 µg/L	1.2 µg/L
31	Devil'S Lake	Forest	-	22 µg/L	2.5 µg/L
32	Wind Lake	Polk	10 ft	17.2 µg/L	-
33	Green Lake	Walworth	11 ft	10.7 µg/L	-
34	Green Lake	Washington	9 ft	16.6 µg/L	-
35	Boulder Lake	Oconto	11 ft	13.3 µg/L	-
36	Spider Lake	Iron	8.5 ft	14.4 µg/L	-
37	Spider Lake	Sawyer	10.5 ft	14.1 µg/L	-
38	Spider Lake	Vilas	10.5 ft	14.1 µg/L	-
39	Pickerel Lake	Forest	10 ft	20.4 µg/L	-
40	Pickerel Lake	Oconto	8 ft	15.6 µg/L	-
41	Pickerel Lake	Vilas	6 ft	23 µg/L	-
42	Pickerel Lake	Lincoln	-	20.3 µg/L	-
43	Carpenter Lake	Vilas	7.5 ft	17 µg/L	-
44	Cranberry Lake	Burnett	8.8 ft	14.1 µg/L	-
45	Beaver Dam Lake	Barron	11 ft	12.9 µg/L	-
46	North Turtle Lake	Vilas	8.5 ft	15.4 µg/L	-
47	Balsam Lake	Washburn	8.8 ft	19.3 µg/L	-
48	Silver Lake	Kenosha	7.1 ft	18.2 µg/L	-
49	Silver Lake	Waukesha	10 ft	11.8 µg/L	-
50	Silver Lake	Waushara	14.8 ft	14.7 µg/L	-

Ranked List

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