Wisconsin Lake Water Quality

Water quality grades for 1,522 monitored lakes across 70 counties.

Wisconsin has 1,522 graded lakes in our dataset, sampled across 70 counties. The Wisconsin DNR runs a Citizen Lake Monitoring Network that contributes a large share of the actual measurements. About 68% of Wisconsin's lakes pull an A — 1,040 top-bracket waters. That high A-share comes mostly from the cold, deep, kettle-formed lakes in the north of the state, which buffer themselves against nutrient inputs.

The state's dominant trophic class is oligotrophic: clear, nutrient-poor, slow-growing. These lakes are also the most sensitive to disturbance — the same volume that buffers them against nutrients also slows recovery if those nutrients arrive in quantity. The cleanest county on average is Menominee (grade A); the most-stressed is La Crosse. The gap between the top and bottom counties is large enough that "Wisconsin lake water quality" hides real local variation.

Rank	Lake	County	Grade	Clarity	Max Depth
1	Geneva Lake	Walworth	A	19 ft	135 ft
2	Lac Courte Oreilles Lake	Sawyer	A	38.7 ft	90 ft
3	Sunset Lake	Portage	A	41 ft	55 ft
4	Sunset Lake	Vilas	A	56.5 ft	30 ft
5	Grindstone Lake	Sawyer	A	57.7 ft	60 ft
6	Middle Sugarbush Lake	Vilas	A	50 ft	57 ft
7	Irving Lake	Vilas	A	36.1 ft	-
8	Windigo Lake	Sawyer	A	36.1 ft	51 ft
9	Towanda Lake	Vilas	A	34.5 ft	27 ft
10	Parker Lake	Adams	A	55.8 ft	36 ft
11	West Bay Lake	Vilas	A	27.9 ft	57 ft
12	West Bay Lake	Vilas	A	19.7 ft	23 ft
13	West Bay Lake	Vilas	A	42.7 ft	31 ft
14	Long Lake	Washburn	A	29.5 ft	-
15	Long Lake	Waushara	A	45.9 ft	71 ft
16	Long Lake	Waupaca	A	44.3 ft	76 ft
17	Long Lake	Burnett	A	68.9 ft	41 ft
18	Long Lake	Lincoln	A	47.7 ft	64 ft
19	Long Lake	Chippewa	A	32.8 ft	101 ft
20	Long Lake	Fond du Lac	A	32.8 ft	47 ft
21	Long Lake	Oneida	A	41 ft	58 ft
22	Long Lake	Bayfield	A	52.5 ft	28 ft
23	Long Lake	Waushara	A	19.7 ft	14 ft
24	Long Lake	Oconto	A	47.6 ft	-
25	Long Lake	Iron	A	18 ft	34 ft

Rank	Lake	County	Grade	Clarity
1	Lower Kelly Lake	Waukesha	F	-
2	Grafton Millpond	Ozaukee	F	-
3	Giltners Lake	Fond du Lac	F	-
4	Thiensville Millpond	Ozaukee	F	-
5	Graber Pond	Dane	F	-
6	County K Marsh Lake	Green Lake	F	-
7	Silver Creek Estuary Lake	Green Lake	F	-
8	Little Yellow Lake	Burnett	F	-
9	Hawthorne Hills South Pond	Dane	F	-
10	Mb-2a Cul Lake	Sawyer	F	-
11	Cathedral Point Pond	Dane	F	-
12	Prairie Oaks Pond	Dane	F	-
13	Gateway Pond	Dane	F	-
14	Outlet To Lake Geneva	Walworth	F	-
15	Silent Street Pond	Dane	F	-
16	Investment Court Pond	Dane	F	-
17	Little St. Germain Lake-West Bay-at St. Germain	Vilas	F	-
18	St. Louis River Outlet Upstream of John A. Blatnik Memorial Bridge Lake	Douglas	F	2.9 ft
19	Pepin Lake	Pepin	F	1.6 ft
20	Tilleda Off Bridge Lake	Shawano	F	1.6 ft
21	Neshonoc Lake	La Crosse	F	1.3 ft
22	Buffalo Lake	Marquette	F	-
23	Frog Lake	Burnett	F	-
24	Lake Denoon	Waukesha	F	1.5 ft
25	Tiedman Pond	Dane	F	1.6 ft

Wisconsin Lake Water Quality

Lake Map

Counties

Top 25 Cleanest Lakes

25 Lakes Needing Attention