Morgan County Lake Quality
Illinois, 2 lakes, average grade D (Poor)
Only 2 lakes in Morgan 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. 1 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 Jacksonville Lake (D); the most-stressed is Mauvaise Terre Lake (F).
Quick Answers for Morgan County
Planning a trip? Check special fishing regulations for Jacksonville Lake — or check the official Illinois fishing regulations.
All Lakes in Morgan County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Jacksonville Lake | D | 1.8 ft | 48 µg/L |
| 2 | Mauvaise Terre Lake | F | - | 162 µg/L |
Other Counties in Illinois
See how Morgan 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 Morgan County
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Source: EPA National Aquatic Resource Surveys, 2026.