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May 2010

Quaggas - A Tiny But Formidable Foe

Click here to view more slides of the quagga mussel.

The quagga mussel is tiny, but its presence is huge—and hugely destructive. Quaggas are an invasive species and a major problem for Metropolitan. But the district has implemented operational efforts to contain them.

Quaggas attach themselves, like crusty suction cups, to under-water structures such as water-utility pumps and pipes, and begin multiplying rapidly. They clog and impede underwater gratings, pumps and pipes.

Arriving in U.S. waters in the 1980s, traveling from Ukraine in the ballast tanks of ocean-going ships, the quaggas quickly colonized.

The dime-sized, freshwater bivalve mollusk, along with the similar zebra mussel, severely affected water utility facilities in the Great Lakes and Mississippi River before it was detected in Lake Mead on the Colorado River in January 2007.

Soon thereafter, the mussels spread through Metropolitan’s Colorado River Aqueduct as far south as Lake Skinner, near Temecula.

However, Diamond Valley Lake in southwestern Riverside County, Metropolitan’s largest reservoir, has remained untouched by quagga mussels, as only State Water Project supplies from Northern California—and none from the Colorado River—have been delivered over the past several years. Quaggas have not yet been detected in State Water Project aqueducts or reservoirs.

Metropolitan installed chlorine tanks near the outfall of Copper Basin reservoir, close to the eastern end of the Colorado River Aqueduct, to concentrate the dosage as it begins its 242-mile trip into the Southern California region.

“We add enough chlorine to the water, as it enters the aqueduct, to establish a residual and to kill the larval form of the mussels,” said Metropolitan water quality manager Mic Stewart.

The chlorine level in the water is about 0.3 milligrams per liter, and slightly higher in the hot summer months when the mussels really thrive, explained Ric De Leon, Metropolitan’s quagga mussel expert.


In addition, Metropolitan has shut down and drained the aqueduct five times in the last four years, undertaking necessary repairs while also causing the mussels to dry out and die due to the lack of water. And the warmer the temperatures, the faster the mussels die, De Leon said. The quaggas are flushed downstream when the aqueduct is refilled and captured in what are called sandtraps.

When the aqueduct is dewatered, Metropolitan divers use high-pressure power-washers to blast quaggas off underwater gratings at the Whitsett Intake pump plant, where water is drawn in from Lake Havasu and other aqueduct facilities.

Metropolitan’s efforts to control the quagga and keep their concentrations low have been successful.  But, the quagga problem is not going away anytime soon and  it continues to require serious attention and on-going containment efforts

This newsletter is produced by the:
Metropolitan Water District of Southern California
700 N. Alameda St.
Los Angeles, CA 90012