Hypereutrophic Lakes in Illinois

52 hypereutrophic lakes in Illinois. 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 Illinois 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	Horsetail Lake	Cook	F	2.2 ft	-	64
2	Long Lake	Lake	F	3.4 ft	-	66
3	Salem Lake	Marion	F	1 ft	-	78
4	Saganashkee Slough Lake	Cook	F	0.8 ft	-	79
5	Glendale Lake	Pope	F	4.8 ft	-	57
6	Vandalia Lake	Fayette	F	1.3 ft	-	73
7	Arrowhead Lake	Cook	F	2.1 ft	-	63
8	Bullfrog Lake	Cook	F	1.4 ft	-	72
9	Holiday Shores Lake	Madison	F	1.7 ft	-	70
10	Sag Quarry East Lake	Cook	F	5.4 ft	-	60
11	Dutchman Lake	Johnson	F	2.1 ft	-	65
12	Forbes Lake	Marion	F	1.4 ft	-	74
13	Mermet Lake	Massac	F	1.6 ft	-	73
14	Skokie Lagoons Lake	Cook	F	1.6 ft	-	75
15	Randolph Lake	Randolph	F	1.7 ft	-	69
16	Centralia Lake	Marion	F	1.5 ft	-	73
17	Sam Dale Lake	Wayne	F	1.2 ft	-	77
18	Raccoon Lake	Marion	F	1.2 ft	-	78
19	Carlyle Lake	Clinton	F	1.8 ft	-	73
20	Midlothian Lake	Cook	F	1.2 ft	-	73
21	Slm Side Channel Lake	St. Clair	F	0.8 ft	-	81
22	Fairfield Lake	Wayne	F	1.3 ft	-	72
23	Sparta Northwest Lake	Randolph	F	2.6 ft	-	62
24	Glenn Shoals Lake	Montgomery	F	1 ft	-	74
25	Mattoon Lake	Cumberland	F	1.3 ft	-	78
26	Sara Lake	Effingham	F	2.2 ft	-	65
27	Otter Lake	Macoupin	F	1.8 ft	-	67
28	Lou Yaeger Lake	Montgomery	F	1.8 ft	-	75
29	Grass Lake	Lake	F	1.4 ft	-	70
30	Newton Lake	Jasper	F	1.7 ft	-	70
31	Governor Bond Lake	Bond	F	1.2 ft	-	76
32	Nashville City Lake	Washington	F	1.3 ft	-	81
33	Marie Lake	Lake	F	2.7 ft	-	66
34	Jacksonville Lake	Morgan	F	1.8 ft	-	66
35	Highland Silver Lake	Madison	F	1.3 ft	-	72
36	Pistakee Lake	McHenry	F	2.7 ft	-	65
37	Canton Lake	Fulton	F	2.5 ft	-	65
38	Kinmundy Old Lake	Marion	F	1.5 ft	-	78
39	Nippersink Lake	Lake	F	1.3 ft	-	70
40	Kinmundy New Lake	Marion	F	2.9 ft	-	63
41	Coulterville Lake	Randolph	F	2.7 ft	-	75
42	Paradise Lake	Pike	F	-	-	78
43	Paradise Lake	Coles	F	-	-	74
44	Charleston Side Channel Lake	Coles	F	-	-	72
45	Loveless Lake	Macoupin	F	-	-	67
46	Vermont City Lake	McDonough	F	-	-	71
47	Mauvaise Terre Lake	Morgan	F	-	-	74
48	Diamond Lake	Lake	F	-	-	71
49	Valley Lake	Lake	F	-	-	69
50	Louise Lake	Lake	F	-	-	74
51	Slocum Lake	Lake	F	-	-	75
52	Island Lake	McHenry	F	-	-	79

All hypereutrophic lakes →Minnesota version →Wisconsin 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 →Ontario version →Québec version →All Illinois lakes →

Source: EPA National Aquatic Resource Surveys, 2026.