Lakes With Algae Readings in Illinois
50 lakes in Illinois report elevated algae levels (chlorophyll-a above 20 µg/L). These lakes are most likely to develop blue-green algae blooms during warm, calm summer weather. Avoid swimming during visible blooms and rinse pets after contact.
Ranked List
| # | Lake | County | Clarity | Phosphorus | Algae | |
|---|---|---|---|---|---|---|
| 1 | Quiver Lake | Mason | — | - | - | 140 µg/L |
| 2 | Island Lake | McHenry | — | - | - | 136.5 µg/L |
| 3 | Boujan Swale Lake | Cass | — | - | - | 136 µg/L |
| 4 | Bullfrog Lake | Cook | — | 1.4 ft | 73 µg/L | 124.5 µg/L |
| 5 | Kinmundy Old Lake | Marion | — | 1.5 ft | 277 µg/L | 114.8 µg/L |
| 6 | Saganashkee Slough Lake | Cook | — | 0.8 ft | 170 µg/L | 108.5 µg/L |
| 7 | Slm Side Channel Lake | St. Clair | — | 0.8 ft | 317 µg/L | 95.6 µg/L |
| 8 | Sam Dale Lake | Wayne | — | 1.2 ft | 206 µg/L | 95.2 µg/L |
| 9 | Governor Bond Lake | Bond | — | 1.2 ft | 175 µg/L | 91 µg/L |
| 10 | Slocum Lake | Lake | — | - | - | 90.3 µg/L |
| 11 | Nashville City Lake | Washington | — | 1.3 ft | 606 µg/L | 89.3 µg/L |
| 12 | Mermet Lake | Massac | — | 1.6 ft | 131 µg/L | 88.5 µg/L |
| 13 | Mattoon Lake | Cumberland | — | 1.3 ft | 294 µg/L | 87.1 µg/L |
| 14 | Vandalia Lake | Fayette | — | 1.3 ft | 103.5 µg/L | 84.4 µg/L |
| 15 | Louise Lake | Lake | — | - | - | 80.2 µg/L |
| 16 | Salem Lake | Marion | — | 1 ft | 234 µg/L | 77.5 µg/L |
| 17 | Forbes Lake | Marion | — | 1.4 ft | 140.5 µg/L | 75.9 µg/L |
| 18 | Skokie Lagoons Lake | Cook | — | 1.6 ft | 229 µg/L | 74.7 µg/L |
| 19 | Raccoon Lake | Marion | — | 1.2 ft | 285 µg/L | 73.5 µg/L |
| 20 | Lou Yaeger Lake | Montgomery | — | 1.8 ft | 255 µg/L | 72.6 µg/L |
| 21 | Glenn Shoals Lake | Montgomery | — | 1 ft | 122 µg/L | 72.1 µg/L |
| 22 | Centralia Lake | Marion | — | 1.5 ft | 132 µg/L | 69.7 µg/L |
| 23 | Paradise Lake | Pike | — | - | 245 µg/L | 68.5 µg/L |
| 24 | Diamond Lake | Lake | — | - | - | 63.6 µg/L |
| 25 | Mauvaise Terre Lake | Morgan | — | - | 163.5 µg/L | 62 µg/L |
| 26 | Midlothian Lake | Cook | — | 1.2 ft | 121 µg/L | 61.5 µg/L |
| 27 | Petite Lake | Lake | — | 2.5 ft | 70 µg/L | 59 µg/L |
| 28 | Highland Silver Lake | Madison | — | 1.3 ft | 123 µg/L | 57.3 µg/L |
| 29 | Long Lake | Lake | — | 3.4 ft | 81 µg/L | 57.1 µg/L |
| 30 | Charleston Side Channel Lake | Coles | — | - | 121 µg/L | 56.1 µg/L |
| 31 | Marie Lake | Lake | — | 2.7 ft | 76 µg/L | 55 µg/L |
| 32 | Coulterville Lake | Randolph | — | 2.7 ft | 452.5 µg/L | 51 µg/L |
| 33 | Valley Lake | Lake | — | - | - | 50.7 µg/L |
| 34 | Newton Lake | Jasper | — | 1.7 ft | 116 µg/L | 46.8 µg/L |
| 35 | Canton Lake | Fulton | — | 2.5 ft | 65 µg/L | 46.1 µg/L |
| 36 | Vermont City Lake | McDonough | — | - | 130.5 µg/L | 45.8 µg/L |
| 37 | Randolph Lake | Randolph | — | 1.7 ft | 87.5 µg/L | 44.9 µg/L |
| 38 | Paradise Lake | Coles | — | - | 215.5 µg/L | 42.3 µg/L |
| 39 | Jacksonville Lake | Morgan | — | 1.8 ft | 60.5 µg/L | 42.2 µg/L |
| 40 | Horsetail Lake | Cook | — | 2.2 ft | 45 µg/L | 39.6 µg/L |
| 41 | Pistakee Lake | McHenry | — | 2.7 ft | 74 µg/L | 39.4 µg/L |
| 42 | Carlyle Lake | Clinton | — | 1.8 ft | 238.5 µg/L | 38.8 µg/L |
| 43 | Glendale Lake | Pope | — | 4.8 ft | 23 µg/L | 38 µg/L |
| 44 | Kinmundy New Lake | Marion | — | 2.9 ft | 49.5 µg/L | 38 µg/L |
| 45 | Arrowhead Lake | Cook | — | 2.1 ft | 38 µg/L | 37.6 µg/L |
| 46 | Sag Quarry East Lake | Cook | — | 5.4 ft | 49 µg/L | 37.5 µg/L |
| 47 | Loveless Lake | Macoupin | — | - | 82 µg/L | 37.3 µg/L |
| 48 | Grass Lake | Lake | — | 1.4 ft | 103.5 µg/L | 37.1 µg/L |
| 49 | Nippersink Lake | Lake | — | 1.3 ft | 88 µg/L | 36.6 µg/L |
| 50 | Dutchman Lake | Johnson | — | 2.1 ft | 59.5 µg/L | 35.9 µg/L |
More Answers for Illinois
Get Illinois water-quality updates
New readings can change this ranking. Unsubscribe anytime.