Greene County Lake Quality
Illinois, 3 lakes, average grade D (Nutrient-rich)
Greene County has 3 monitored 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. 1 of those lake carry an A–F grade. The county-level summary describes that subset, not every water body listed. 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 Greenfield Lake (D); the most-stressed is Greenfield Lake (D).
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Quick Answers for Greene County
Planning a trip? Check special fishing regulations for Greenfield Lake — or check the official Illinois fishing regulations.
All Lakes in Greene County
3 lakes · 1 graded, 2 not rated1 graded lake · 2 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | DGreenfield LakeGreene | D | No recent samples | 85.5 µg/L | 30 µg/L | No recent samples | ✓ Public |
| NRBrushy LakeGreene | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRWhite Hall ReservoirGreene | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded |
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 Greene 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.