Johnson County, Kansas: drinking water report. Johnson County is the most populous county in Kansas, home to about 620,000 residents in the Kansas City…
Johnson County is the most populous county in Kansas, home to about 620,000 residents in the Kansas City metro's southern suburbs. Water comes primarily from the Missouri River, treated by WaterOne (formerly Johnson County Water District #1), one of the largest water utilities in the Kansas City region. Some western communities also draw from the Kansas River or local wells.
The Missouri River is one of the longest rivers in North America and carries agricultural runoff from across the Great Plains. WaterOne's treatment process handles the river's variable quality, including seasonal spikes in turbidity and organic content. The utility has invested in ozone treatment and biologically active filtration to manage these challenges.
UCMR5 data shows low-level PFAS detections in the WaterOne system. Johnson County does not host major military installations. According to the Kansas Department of Health and Environment's 2024 compliance data, WaterOne met all federal contaminant limits. Atrazine – a widely used agricultural herbicide – is a more relevant seasonal contaminant in Missouri River water, though treatment reduces it to below MCLs.
Johnson County benefits from a well-funded, well-managed utility. Seasonal variation in source water quality is the main dynamic to be aware of.
Check your water for current data in your area. An activated carbon filter handles taste, atrazine residuals, and provides some PFAS reduction. Our water filter guide covers options. Pull your detailed report, and visit our Kansas page for statewide data.