LAS VEGAS — Invasive quagga mussels are adapting well to life in the desert, especially in Lake Havasu, where scientists have determined their reproduction rate is three times faster than when the pesky mollusks infested the Great Lakes years ago.

Leonard Willett, the Bureau of Reclamation's quagga mussel coordinator for the lower Colorado River dams, said the effort to deal with quaggas, which were discovered last year first in Lake Mead and later downstream of Hoover Dam, still is in the monitoring phase, the first part of what he called the "reactive approach."

"Reactive approach means you're going to live with the mussels. You're going to control them, but you're going to live with them," he said in a recent presentation to the Lake Mead Water Quality Forum.

He projected that as the infestation sets in and begins to clog hydroelectric power cooling pipes and other hardware in Hoover Dam's operations, the maintenance-and-control bill could reach $1 million a year, especially if pipes get plugged with quagga colonies.

That could cause turbines to overheat and shut down until cooling pipes can be cleared of the invasive species.

"This is an evil critter, not good," Willett said. "It is going to cause a lot of problems when we're going to have to install control measures."

Among the options for controlling the invasion is to use a bacteria product that targets the quagga mussels.

While that method still is being developed, Willett said it looked promising.

Other choices are mechanical filters and using chemicals like chlorine to kill them, or a combination of filters and ultraviolet light.

At the end of the day, though, there would be shells from dead quaggas to dispose of and discharge permits to obtain.

So far, conditions for quaggas to thrive appear to be more than adequate at Davis Dam at the south end of Lake Mohave, north of Laughlin.

In October, a colony coated the dam's exterior penstock gate like carpeting.

A month later, downstream at Parker Dam on Lake Havasu, quaggas covered sampling plates used to monitor them.

"At Parker Dam, there is a lot of colonization. At Parker, there is no hope. They colonize repeatedly," Willett said.

With warmer year-round temperatures than bodies of water in the Great Lakes, quaggas are able to reproduce six times a year instead of two.

In addition, Havasu has the right mix of food, calcium and dissolved oxygen to sustain colonization.

With that, Willett said, "You're going to get mussels. I'm not surprised."

Near Hoover Dam, quaggas have been found more than 200 feet deep in Lake Mead.

Not only do they pose a threat to the cooling pipe system for hydroelectric turbines, but also to the network that supplies domestic water for workers and visitors at the dam.

They prefer to cling to flat, stainless steel structures where water flows slower than 6 feet per second.

"Mussels really like stainless steel. They don't like copper or brass," Willett said.

The Casitas Municipal Water District fears the mussel could turn up at Lake Casitas. The agency is wrestling with the idea of temporarily closing the lake to the roughly 30,000 outside boats that annually launch there. Board members are afraid the mussel will attach itself to a boat transported from an infected lake to Lake Casitas, causing untold environmental and economic damage.