Hypereutrophic Lakes in Wisconsin

52 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. 52 hypereutrophic lakes are on the Wisconsin books. Almost none of them are deep — 0% 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	-	71
2	Beaver Dam Lake	Dodge	F	1 ft	-	80
3	Rice Lake	Dane	F	1.5 ft	-	76
4	Rice Lake	Oneida	F	1.5 ft	-	71
5	Indian Lake	Dane	F	0.7 ft	-	84
6	Big Eau Pleine Lake	Marathon	F	1.5 ft	-	73
7	Dairyland Reservoir	Rusk	F	1.4 ft	-	73
8	Duck Lake	Bayfield	F	1.6 ft	-	71
9	Eagle Lake	Racine	F	1.5 ft	-	72
10	Comus Lake	Walworth	F	1.5 ft	-	76
11	Fox Lake	Dodge	F	1.7 ft	-	70
12	Lake Koshkonong	Jefferson	F	1.7 ft	-	77
13	Ludden Lake	Iowa	F	1.5 ft	-	75
14	Beckers Lake	Calumet	F	1.5 ft	-	73
15	Mason Lake	Adams	F	1.1 ft	-	73
16	Tiedman Pond	Dane	F	0.3 ft	-	96
17	Upper Vermillion Lake	Barron	F	1.7 ft	-	73
18	Odana Pond	Dane	F	1 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	1.2 ft	-	76
22	Mead Lake	Clark	F	2 ft	-	74
23	Chilton Millpond	Calumet	F	2.9 ft	-	74
24	Forestville Flowage Lake	Door	F	1 ft	-	77
25	Big Eau Pleine Southeast Point Lake	Marathon	F	1.5 ft	-	71
26	Neshonoc Lake	La Crosse	F	0.4 ft	-	91
27	Eddy by Pony Creek Lake	Shawano	F	0.5 ft	-	98
28	Tilleda Off Bridge Lake	Shawano	F	0.5 ft	-	91
29	Little Lake Butte des Morts	Winnebago	F	2 ft	-	71
30	Garner Lake	Richland	F	1.3 ft	-	73
31	Little Twin Lake	Green Lake	F	1.5 ft	-	71
32	Pepin Lake	Pepin	F	1.6 ft	-	71
33	Jennie Weber Lake	Oneida	F	1.5 ft	-	71
34	Dexter Lake	Wood	F	1.5 ft	-	82
35	Little St. Germain Lake-West Bay-at St. Germain	Vilas	F	-	-	83
36	Investment Court Pond	Dane	F	-	-	92
37	Silent Street Pond	Dane	F	-	-	94
38	Outlet To Lake Geneva	Walworth	F	-	-	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	-	-	73
43	Lake Tomah	Monroe	F	-	-	75
44	Mb-2a Cul Lake	Sawyer	F	-	-	82
45	Hawthorne Hills South Pond	Dane	F	-	-	80
46	Silver Creek Estuary Lake	Green Lake	F	-	-	73
47	County K Marsh Lake	Green Lake	F	-	-	76
48	Graber Pond	Dane	F	-	-	83
49	Thiensville Millpond	Ozaukee	F	-	-	78
50	Giltners Lake	Fond du Lac	F	-	-	77
51	Grafton Millpond	Ozaukee	F	-	-	72
52	Lower Kelly Lake	Waukesha	F	-	-	77

All hypereutrophic lakes (MN+WI) →Minnesota version →All Wisconsin lakes →

Source: EPA National Aquatic Resource Surveys, 2026.