Wichita ? City water officials are relieved to find that zebra mussel larvae discovered in high numbers last August in Cheney Reservoir – where Wichita gets about 60 percent of its water – have disappeared.

That’s in sharp contrast to El Dorado Reservoir, where zebra mussels continue to thrive.

Zebra mussels can clog water intake structures, coat rocks with sharp shells and outcompete young fish for the plankton on which they feed.

“It’s good they don’t seem to be in (Cheney),” said Mike Carney, superintendent of production and pumping for Wichita’s water department.

Jason Goeckler, an aquatic nuisance species specialist with the Kansas Department of Wildlife and Parks, said no larvae where found at Cheney in tests earlier this month. Several tests last fall also were negative.

“I’m not ready to give the all-clear, but we’re starting to feel better,” Goeckler said.

At El Dorado, where zebra mussels first were found in August 2003, they spread throughout the lake in a few months. So far, they have not hurt the city’s ability to draw water from the reservoir, but they have caused other problems, said Kurt Bookout, with the El Dorado water department.

It’s up to anglers and boaters to help prevent the spread of zebra mussels from El Dorado to Cheney, Goeckler said.

The mussels have moved into about 20 states in recent years, causing millions of dollars of damage by clogging intake structures for water supply plants.

Biologists think zebra mussels or their larvae are transported in water or vegetation hauled by ships, boats or boat trailers.

Those problems could easily occur at Cheney if zebra mussels were to become established there, officials said.