Hypereutrophic Lakes in Wisconsin

51 hypereutrophic lakes in Wisconsin. Very high nutrients, dense algae, poor clarity.

Hypereutrophic lakes (TSI above 70) are at the upper end of the productivity scale: visible algal blooms most weeks of summer, clarity often under 3 feet, and meaningful risk of harmful-algal-bloom toxin events. 51 hypereutrophic lakes are on the Wisconsin books. Almost none of them are deep — 12% break 50 feet. Shallow basin plus heavy nutrient input is the consistent recipe.

Hypereutrophic lakes overwhelmingly grade D or F — the trophic class and the grade are measuring closely-related dimensions of the same underlying nutrient regime.

#	Lake	County	Grade	Clarity	Depth	TSI
1	Lazy Lake	Columbia	D	4 ft	8 ft	71
2	Silver Lake	Manitowoc	F	-	-	83
3	Indian Lake	Dane	F	0.7 ft	-	84
4	Big Eau Pleine Lake	Marathon	F	1.5 ft	-	73
5	Beaver Dam Lake	Dodge	F	1 ft	-	80
6	Rice Lake	Dane	F	1.5 ft	8 ft	76
7	Rice Lake	Oneida	F	1.5 ft	3 ft	71
8	Dairyland Reservoir	Rusk	F	1.4 ft	70 ft	73
9	Duck Lake	Bayfield	F	1.6 ft	30 ft	71
10	Eagle Lake	Racine	F	1.5 ft	11 ft	72
11	Comus Lake	Walworth	F	1.5 ft	6 ft	76
12	Lake Koshkonong	Jefferson	F	1.7 ft	7 ft	77
13	Ludden Lake	Iowa	F	1.5 ft	14 ft	75
14	Beckers Lake	Calumet	F	1.5 ft	52.5 ft	73
15	Mason Lake	Adams	F	1.1 ft	9 ft	73
16	Tiedman Pond	Dane	F	0.3 ft	-	96
17	Upper Vermillion Lake	Barron	F	1.7 ft	9 ft	73
18	Odana Pond	Dane	F	1 ft	5 ft	82
19	Unnamed Lake	Crawford	F	1.2 ft	-	74
20	Unnamed Lake	Clark	F	1.3 ft	-	73
21	Yellowstone Lake	Lafayette	F	1.3 ft	14 ft	75
22	Mead Lake	Clark	F	2 ft	16 ft	74
23	Forestville Flowage Lake	Door	F	1 ft	5 ft	77
24	Chilton Millpond	Calumet	F	2.9 ft	7 ft	74
25	Big Eau Pleine Southeast Point Lake	Marathon	F	1.5 ft	46 ft	71
26	Neshonoc Lake	La Crosse	F	0.4 ft	-	91
27	Eddy by Pony Creek Lake	Shawano	F	0.5 ft	11 ft	98
28	Tilleda Off Bridge Lake	Shawano	F	0.5 ft	11 ft	91
29	Little Lake Butte des Morts	Winnebago	F	2 ft	18 ft	71
30	Garner Lake	Richland	F	1.3 ft	8 ft	73
31	Little Twin Lake	Green Lake	F	1.5 ft	-	71
32	Pepin Lake	Pepin	F	1.5 ft	60 ft	71
33	Jennie Weber Lake	Oneida	F	1.5 ft	8 ft	71
34	Dexter Lake	Wood	F	1.5 ft	17 ft	82
35	Little St. Germain Lake-West Bay-at St. Germain	Vilas	F	-	53 ft	83
36	Investment Court Pond	Dane	F	-	-	92
37	Silent Street Pond	Dane	F	-	-	94
38	Outlet To Lake Geneva	Walworth	F	-	135 ft	99
39	Gateway Pond	Dane	F	-	-	87
40	Prairie Oaks Pond	Dane	F	-	-	89
41	Cathedral Point Pond	Dane	F	-	-	84
42	Decorah Lake	Juneau	F	-	15 ft	73
43	Lake Tomah	Monroe	F	-	19 ft	75
44	Hawthorne Hills South Pond	Dane	F	-	-	80
45	County K Marsh Lake	Green Lake	F	-	-	76
46	Silver Creek Estuary Lake	Green Lake	F	-	236 ft	73
47	Graber Pond	Dane	F	-	-	83
48	Thiensville Millpond	Ozaukee	F	-	-	78
49	Giltners Lake	Fond du Lac	F	-	13 ft	77
50	Grafton Millpond	Ozaukee	F	-	-	72
51	Lower Kelly Lake	Waukesha	F	-	36 ft	77

All hypereutrophic lakes →Minnesota version →Illinois version →Michigan version →Iowa version →Ohio version →Pennsylvania version →New York version →Missouri version →Indiana version →North Dakota version →South Dakota version →Florida version →Colorado version →North Carolina version →Vermont version →Texas version →Oregon version →Arkansas version →Oklahoma version →Kansas version →Nebraska version →Nevada version →Arizona version →Idaho version →Montana version →New Mexico version →Tennessee version →Alabama version →Virginia version →Kentucky version →Utah version →Washington version →Wyoming version →Georgia version →Massachusetts version →All Wisconsin lakes →

Source: EPA National Aquatic Resource Surveys, 2026.