Calwell's group is one of at least two that takes people out on the river, and several businesses rent canoes or kayaks for between $20 and $70 a day.
Ryan O'Neill, a 21-year-old junior in animal science at Kansas State University, began renting out his seven kayaks just this year after hearing from people wanting to explore the river.
"The scenery, there is something about it," O'Neill, who calls his business Mudkat Kayaking, mused. "Especially in the Flint Hills part. It's rolling hills, and as far as the river itself, it's really sandy and nice. It's not necessarily moving fast, so you can get out of your boat and look around and get into the water."
When planning a trip, keep in mind that some stretches of the river are more pristine than others. While debris like old tires and sand and gravel dredging operations mar some areas, other spans of the river are unsullied.
Calwell recommends monitoring wind speeds and the flow of water before departing, and watching out for dams. One low-water dam near a water treatment plant in Topeka has been particularly treacherous, killing a kayaker in July 2011 and two canoers in August 2007. Topeka already has added warning signs and a paved pathway where paddlers can portage their vessels to get around it. In mid-August, $50,000 was approved to study ways to make the dam safer, city spokesman David Bevens said. River enthusiasts eventually would like to see the dam transformed into a whitewater run.
"We recognize that the river is becoming more popular as a recreation outlet, and we are working with the public to make it as safe as possible around our water intake area and low-water dam," Bevens said.
Another project in the downstream town of Lawrence, home to the University of Kansas, has paddlers excited. As part of a hydroelectric plant that's under construction, Bowersock Mills & Power Co. plans to add a portage area by spring 2014 where people can pull out their canoes or kayaks and carry them around a downtown-area dam. The area already is popular among kayakers who like to play in the waves below the power house of the company's existing hydroelectric plant.