The Kansas River, known locally as the Kaw, begins at the confluence of the Republican and Smoky Hill Rivers near Junction City, Kansas, and flows 173 miles to Kansas City, where it joins the Missouri River at Kansas City, Kansas. The Kaw drains almost the entire northern half of Kansas, as well as part of Nebraska and Colorado (53,000 square miles). It is the largest prairie‐based river system in the world, with the watershed comprised primarily of grassland, pastures, and row‐crop agriculture. 

The Kaw serves as a critical drinking water supply for more than 800,000 people. Additionally, the Kaw is used for irrigation, municipal wastewater and industrial discharges, cooling water for three coal‐fired power plants, and as a source of commercial sand and gravel. The Kaw is popular for canoeing and kayaking, and has an access point almost every ten miles for its entire length. In 2012, it was added to the National Park Service’s National Water Trail System.

There are nine major reservoirs within the lower end of the drainage basin. In total, 18 Federal reservoir projects impound water on all major tributaries of the Kansas River and control streamflow in 85 percent of the drainage area. From the confluence, the left bank tributaries and associated reservoirs include the Republican (Harlan and Lovewell – Upper Republican; Milford – Lower Republican), Big Blue (Tuttle Creek), and Delaware (Perry). The right bank tributaries and associated reservoirs include the Smoky Hill (Waconda, Wilson, Kanopolis), and Wakarusa Rivers (Clinton). Other, smaller reservoirs managed by the Bureau of Reclamation and states of Kansas and Nebraska are also part of regulating flows in the upper reaches of the basin.

The average discharge on the Kansas River is in the range of 7,200 cfs. However, the range has been from as high as 133,000 cfs to as low as 353 cfs. The Kansas River is generally free flowing but has some diversion weirs and a low-head hydroelectric dam. There are numerous small tributaries that contribute unregulated flow to the river. 

Federally constructed flood risk management features are located along segments of the river that pass through Topeka and along the lower reach near the confluence with the Missouri River.

The Kansas River is an important water source and has numerous sources of pollution, including nutrients, bacteria, sediment, and pesticides. Reservoir sedimentation is of heightened concern on the reservoirs due to impacts on the yield from water supply storage, increased maintenance costs, and potential future impacts on flood control and recreation. Bluegreen algae is an ongoing concern for water supply, public health, and recreation. Bank erosion occurs along some segments of the river where channel degradation has occurred.