Shawnee County, Kansas: drinking water report. Shawnee County is home to Topeka, Kansas's state capital, with a population of about 178,000.
Shawnee County is home to Topeka, Kansas's state capital, with a population of about 178,000. The City of Topeka draws water from the Kansas (Kaw) River and treats it at the Oakland and Dornwood treatment plants. The Kansas River drains the entire north-central portion of the state, carrying agricultural runoff from one of the most intensively farmed regions in the country. Forbes Field Air National Guard Base operates on the southeast edge of the city.
Atrazine in the Kansas River is a recurring compliance challenge. According to the Kansas DHE's 2024 monitoring data, raw water atrazine concentrations at Topeka's intake exceeded 3 ppb – the EPA's MCL – on 18 days during the spring 2024 season. The treatment plants use powdered activated carbon to reduce atrazine to compliant levels during peak events, but this adds significant cost.
Forbes Field has confirmed AFFF use and PFAS contamination. The EPA's UCMR5 data shows PFAS detections in the Topeka system. A 2024 KDHE investigation documented PFAS in groundwater monitoring wells near Forbes at concentrations up to 60 ppt for PFOS. One public water system well near the base has been taken offline.
Spring is the critical season for water quality in Shawnee County. Heavy rains wash herbicides from upstream farmland into the Kansas River, and the treatment system works hardest during this period.
Check your water for current data on your area. For atrazine and disinfection byproducts, activated carbon filters are effective. For PFAS, reverse osmosis provides broader protection. Our water filter guide covers both scenarios. Pull your detailed report for seasonal trends, and visit our Kansas page for statewide context.