Wichita ? Adult zebra mussels were discovered this week at Cheney Reservoir, making Cheney the third Kansas lake contaminated with the destructive species that can cause problems for swimmers, boaters and the public water system.

“It’s not what we wanted to hear, but it’s not a total surprise,” said Jerry Blain, water department superintendent of production and pumping. “We’ve already done a study on what our options might be, and none of them are free.”

Zebra mussels are notorious for clogging the intake structures at water and power plants and damaging native fish populations. Cheney Reservoir, about 20 miles west of Wichita, provides about 70 percent of the city’s water.

Jon Stein, a Kansas Department of Wildlife and Parks fisheries biologist, found about 35 zebra mussels scattered over the lake’s southern end Wednesday.

They were first found in Kansas on a section of El Dorado Reservoir shoreline in 2003 and were soon found lakewide.

Jason Goeckler, Wildlife and Parks aquatic nuisance species coordinator, said densities up to 64,000 adults per square meter have since been found attached to some rocks, logs and bridge pilings at El Dorado.

The sharp-shelled mussels have made wading and swimming hazardous, leaving cuts on unprotected feet and hands. Biologists also suspect they have damaged fish populations by out-competing bait fish and young game fish for plankton and other food.

They’ve also been found within the city of El Dorado’s water intake system at the lake but have caused no major problems.

Last winter they were found in the Winfield City Lake.

Officials say they were probably unknowingly carried to El Dorado and Cheney by boaters.

Wildlife and Parks has asked El Dorado anglers and boaters to carefully drain all water from boat motors and bait buckets before leaving the lake.