Hypereutrophic Lakes in Illinois

38 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. 38 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	Bluff Lake	Lake	D	4 ft	-	72
2	Bode Lake North	Cook	F	1.5 ft	-	71
3	Belly Deep Slough Lake	Cook	F	0.7 ft	-	83
4	Sauk Lake	Cook	F	1 ft	-	77
5	Washington Park Lagoon Lake	Cook	F	1.4 ft	-	72
6	Sherman Park Lagoon Lake	Cook	F	1.3 ft	-	73
7	Humboldt Park Lagoon Lake	Cook	F	1.5 ft	-	71
8	Garfield Park Lagoon Lake	Cook	F	1.5 ft	-	71
9	Douglass Park Lagoon Lake	Cook	F	1.5 ft	-	71
10	Mckinley Park Lagoon Lake	Cook	F	1.5 ft	-	71
11	Big Marsh Lake	Cook	F	1 ft	-	77
12	Salem Lake	Marion	F	1 ft	-	79
13	Lake Springfield	Sangamon	F	1.5 ft	-	71
14	Saganashkee Slough Lake	Cook	F	0.8 ft	-	75
15	Vandalia Lake	Fayette	F	1.3 ft	-	72
16	Holiday Shores Lake	Madison	F	1.7 ft	-	72
17	Skokie Lagoons Lake	Cook	F	1.6 ft	-	74
18	Sam Dale Lake	Wayne	F	1.2 ft	-	75
19	Raccoon Lake	Marion	F	1.2 ft	-	78
20	Carlyle Lake	Clinton	F	1.8 ft	-	75
21	Slm Side Channel Lake	St. Clair	F	0.8 ft	-	82
22	Fairfield Lake	Wayne	F	1.3 ft	-	73
23	Glenn Shoals Lake	Montgomery	F	1 ft	-	73
24	Mattoon Lake	Cumberland	F	1.3 ft	-	77
25	Lou Yaeger Lake	Montgomery	F	1.8 ft	-	75
26	Decatur Lake	Macon	F	1.3 ft	-	71
27	Governor Bond Lake	Bond	F	1.2 ft	-	74
28	Nashville City Lake	Washington	F	1.3 ft	-	84
29	Highland Silver Lake	Madison	F	1.3 ft	-	72
30	Borah Lake	Richland	F	2.2 ft	-	70
31	Kinmundy Old Lake	Marion	F	1.5 ft	-	76
32	Coulterville Lake	Randolph	F	2.7 ft	-	77
33	Paradise Lake	Pike	F	-	-	77
34	Paradise Lake	Coles	F	-	-	75
35	Vermont City Lake	McDonough	F	-	-	71
36	Mauvaise Terre Lake	Morgan	F	-	-	78
37	Quiver Lake	Mason	F	-	-	79
38	Boujan Swale Lake	Cass	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 →All Illinois lakes →

Source: EPA National Aquatic Resource Surveys, 2026.