DeKalb County Lake Quality
Illinois, 1 lake, average grade B (Good)
DeKalb County holds 1 monitored lake. With a sample that small the county-level summary describes those specific waters, not necessarily every water body in the county. Every one of those lake carries an A–F grade, so the county-level summary covers the full set rather than a monitored subset. With an average grade of B, DeKalb County sits comfortably above the Illinois median.
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. Shabbona Lake (B) is the cleanest in the county.
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Quick Answers for DeKalb County
Planning a trip? Check special fishing regulations for Shabbona Lake — or check the official Illinois fishing regulations.
All Lakes in DeKalb County
1 lake1 graded lake
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | BShabbona LakeDeKalb | B | 4.9 ft | 28 µg/L | 13.3 µg/L | No recent samples | ✓ Public |
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Other Counties in Illinois
See how DeKalb 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.