Johnson County Lake Quality
Indiana, 4 lakes, average grade D (Poor)
Johnson County has 4 graded 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. 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 Lamb Lake (C); the most-stressed is Lamb Lake (C).
Quick Answers for Johnson County
Planning a trip? Check special fishing regulations for Lamb Lake — or check the official Indiana fishing regulations.
All Lakes in Johnson County
| Rank | Lake | Grade | Clarity | Phosphorus |
|---|---|---|---|---|
| 1 | Lamb Lake | C | 7.2 ft | - |
Other Counties in Indiana
See how Johnson 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 Johnson County
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Source: EPA National Aquatic Resource Surveys, 2026.