An invasive mollusk found in a water-diversion channel east of Mesa could clog pipes, jam mechanical equipment, increase maintenance costs on water-distribution systems in Arizona and alter riparian ecosystems.
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Experts say the thumbnail-sized quagga mussels could use the Phoenix metropolitan area's network of canals to spread farther into Arizona and possibly damage water-treatment plants.
The canals supply water for most Phoenix-area communities, at least two power plants, more than a dozen urban lakes and thousands of customers of farm and residential irrigation.
Salt River Project workers found 11 quagga mussels earlier this month and four more Wednesday on monitoring lines near Granite Reef Dam, where water is diverted into the canals.
Experts say one female quagga can produce 40,000 eggs in a breeding cycle and up to 1 million eggs in a year.
How many mussels have made their way into the diversion channel or downstream is unknown, but the four found Wednesday had attached themselves since the block was last checked about two weeks ago.
"It means they are able to settle in our canals," said Lesly Swanson, an environmental scientist for SRP. "We knew they had been coming in from the (Central Arizona Project Canal) for a while. It's really a question of why we haven't found them sooner."
Quaggas have colonized the lower Colorado River since they were discovered in January 2007. Especially hard hit is Lake Havasu, the source of water for the CAP Canal, which moves water to Phoenix and Tucson.
SRP will take a closer look at canal walls in the coming months during annual maintenance, when lengths of the waterways are drained for several weeks.
The utility plans to meet with its municipal customers to discuss how they can protect the treatment plants.
The biggest fear is that mussels could attach themselves to intake pipes and block the flow of water into a treatment plant. That would increase maintenance costs at a time when municipal budgets are strained.
Most communities say they are aware of the threat and have begun taking steps on their own, though few have begun to calculate the added costs if mussels fill pipes.