Macoupin County Lake Quality
Illinois, 3 lakes, average grade D (Poor)
Only 3 lakes in Macoupin County carry an active grade. The county-level summary is therefore representative of those specific lakes, not necessarily of every water body in the county. The county-wide average grade is D — water quality issues are persistent across most of the monitored basins. 0 lakes fall into the F bracket outright.
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 Palmyra-Modesto Lake (C); the most-stressed is Otter Lake (D).
Quick Answers for Macoupin County
Planning a trip? Check special fishing regulations for Palmyra-Modesto Lake — or check the official Illinois fishing regulations.
All Lakes in Macoupin County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Palmyra-Modesto Lake | C | - | 56 µg/L |
| 2 | Otter Lake | D | 1.8 ft | 37 µg/L |
| 3 | Loveless Lake | D | - | 63.5 µg/L |
Other Counties in Illinois
See how Macoupin 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 Macoupin County
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Source: EPA National Aquatic Resource Surveys, 2026.