Johnson County Lake Quality
Kansas, 20 lakes, average grade D (Nutrient-rich)
Johnson County's 20 monitored lakes fall in the moderate-density bracket for Kansas. The county-level average smooths over real differences — a single agricultural watershed near the southwest corner can pull the average down even if the rest of the county runs clean. 13 of those lakes 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. 9 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 New Olathe Lake (B); the most-stressed is Gardner Lake (F).
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Quick Answers for Johnson County
Planning a trip? Check special fishing regulations for New Olathe Lake — or check the official Kansas fishing regulations.
All Lakes in Johnson County
20 lakes · 13 graded, 7 not rated13 graded lakes · 7 not rated, hidden
| # | Lake | Grade | Clarity | Phosphorus | Algae | Trophic | Access |
|---|---|---|---|---|---|---|---|
| 1 | BNew Olathe LakeJohnson | B | 3.4 ft | 29 µg/L | 10 µg/L | No recent samples | Not recorded |
| 2 | COlathe LakeJohnson | C | 3 ft | 50 µg/L | 14.2 µg/L | No recent samples | Not recorded |
| 3 | CLenexa LakeJohnson | C | No recent samples | 29 µg/L | 16.2 µg/L | No recent samples | Not recorded |
| 4 | DStoll Park LakeJohnson | D | No recent samples | 70 µg/L | 22 µg/L | No recent samples | Not recorded |
| 5 | FGardner LakeJohnson | F | 2.3 ft | 37 µg/L | 43.5 µg/L | No recent samples | Not recorded |
| 6 | FCedar LakeJohnson | F | 1.6 ft | 113 µg/L | 39.5 µg/L | No recent samples | Not recorded |
| 7 | FKingston Lake ParkJohnson | F | No recent samples | 129.9 µg/L | 58.7 µg/L | No recent samples | Not recorded |
| 8 | FSar Ko Park LakeJohnson | F | No recent samples | 86.5 µg/L | 51.9 µg/L | No recent samples | Not recorded |
| 9 | FTomahawk Creek Park LakeJohnson | F | No recent samples | 162.1 µg/L | 45.9 µg/L | No recent samples | Not recorded |
| 10 | FSouth LakeJohnson | F | No recent samples | 177.2 µg/L | 72 µg/L | No recent samples | Not recorded |
| 11 | FLeawood Park LakeJohnson | F | No recent samples | 532.8 µg/L | 42.4 µg/L | No recent samples | Not recorded |
| 12 | FWater Works Park LakeJohnson | F | No recent samples | 101.7 µg/L | 107 µg/L | No recent samples | Not recorded |
| 13 | FAntioch Park LakeJohnson | F | No recent samples | 347.1 µg/L | 61.3 µg/L | No recent samples | Not recorded |
| NRShawnee Mission LakeJohnson | NR | 4.3 ft | 20 µg/L | 9.7 µg/L | No recent samples | Not recorded | |
| NRLenexa City LakeJohnson | NR | 2.4 ft | 71 µg/L | 40 µg/L | No recent samples | Not recorded | |
| NRSummer Crest Park LakeJohnson | NR | No recent samples | 109.6 µg/L | 93.5 µg/L | No recent samples | Not recorded | |
| NRErnie Miller Park LakeJohnson | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRHeritage LakeJohnson | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NRSpring Hill City LakeJohnson | NR | No recent samples | No recent samples | No recent samples | No recent samples | Not recorded | |
| NROlathe LakeJohnson | 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 Kansas
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Source: EPA National Aquatic Resource Surveys, 2026.