Macon County Lake Quality
Illinois, 2 lakes, average grade D (Nutrient-rich)
Macon County holds 2 monitored lakes. With a sample that small the county-level summary describes those specific waters, not necessarily every water body in the county. 1 of those lake carry an A–F grade. The county-level summary describes that subset, not every water body listed. On average, Macon County lakes grade D, with phosphorus loading and reduced clarity showing up across most of the dataset.
The county's lakes lean shallow, which makes the grades sensitive to wind, sediment-resuspension, and any nutrient inputs from the watershed. The cleanest lake on the books is Decatur Lake (D); the most-stressed is Decatur Lake (D).
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Quick Answers for Macon County
Planning a trip? Check special fishing regulations for Decatur Lake — or check the official Illinois fishing regulations.
All Lakes in Macon County
2 lakes · 1 graded, 1 not rated1 graded lake · 1 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | DDecatur LakeMacon | D | 1.3 ft | 103 µg/L | 25 µg/L | No recent samples | ✓ Public |
| NRLake DecaturMacon | NR | No recent samples | No recent samples | No recent samples | No recent samples | ✓ Public |
NR = not rated: there is not enough recent sampling to support a letter. That is EPA Integrated Reporting Category 3 (insufficient information), not a failing grade. How grading works.
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Other Counties in Illinois
See how Macon County stacks up in the national county water-quality rankings, or browse the full directory of graded lakes across all United States (49 states), Canada (Ontario, Québec, Nova Scotia, British Columbia and Newfoundland and Labrador), and 38 other country hubs..
Source: EPA National Aquatic Resource Surveys, 2026.