Marion County Lake Quality
Illinois, 6 lakes, average grade F (Very Poor)
Marion County has 6 graded lakes — a thin enough sample that one or two stressed lakes can move the county average noticeably. Use the per-lake pages below for what actually matters. The county average is F — the most-stressed bracket in our rubric. Most monitored lakes here show persistent nutrient loading and algal pressure.
Most of the county's monitored lakes are shallow — under 50 feet — which means wind keeps the water column mixed all summer and sediment-bound phosphorus releases back into the surface layer whenever the bottom is disturbed. Kinmundy New Lake (D) is the cleanest in the county.
Quick Answers for Marion County
Planning a trip? Check special fishing regulations for Kinmundy New Lake — or check the official Illinois fishing regulations.
All Lakes in Marion County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Kinmundy New Lake | D | 2.9 ft | 36.5 µg/L |
| 2 | Forbes Lake | D | 1.4 ft | 74 µg/L |
| 3 | Centralia Lake | D | 1.5 ft | 86.5 µg/L |
| 4 | Salem Lake | F | 1 ft | 197 µg/L |
| 5 | Raccoon Lake | F | 1.2 ft | 202.5 µg/L |
| 6 | Kinmundy Old Lake | F | 1.5 ft | 212.5 µg/L |
Other Counties in Illinois
See how Marion County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all 15 states.
Where to stay near Marion County
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Source: EPA National Aquatic Resource Surveys, 2026.