shueman
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Posted: Mar. 03 2008,6:52 pm |
Post # 1 |
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From the Parker News On-Line...
Quagga mussels a growing threat to Colorado River water system
By John Rudolph
Monday, February 25, 2008 4:05 PM MST
In January 2007, the first quagga mussels were discovered in Lake Havasu. In the year since, the fingernail-sized mollusks have exploded in numbers, reproducing with unprecedented speed and threatening to cause untold damage to the interstate water distribution systems that pull water from the river at the south end of the lake.
As they spread, the invasive mussels may also pose a danger to local fish populations. As filter feeders, they pull sediment out of the water, letting more sunlight through and leading to algae blooms, which can hurt fisheries.
The mussels, native to Eastern Europe, arrived in the Great Lakes in the 1980s, where they eventually caused billions of dollars in damage to power companies and local economies. First spotted in Lake Mead early last year, the mussels have been found to reproduce three times faster than they do in the East, likely due to the Southwest's warmer climate.
The ultimate impact of the mussel invasion is yet to be seen, but biologists warn that the creatures, which can attach to virtually any surface, have the capability to clog pipes and valves at hydroelectric dams and pumping plants.
"All the Colorado River users who take water from the river are going to be dealing with these issues," said Dr. Ric de Leon, microbiology unit manager for the Metropolitan Water District, and head of the district's quagga mussel control program. "These mussels grow to very high numbers, so as a water conveyer, it becomes an issue that they will begin interfering with water conveyance,"
In Lake Havasu, the invasive mussels are attaching themselves to the intake valves of the Metropolitan Water District's Whitsett Intake Plant, which distributes water to 18 million people in Southern California. For several months, workers from the plant have been donning wetsuits to clean the valves, blasting away the creatures with high-pressure hoses.
"Some areas will have hundreds per square meter," said de Leon. "Other areas will have in the thousands per square meter."
Mussels have been detected at Parker Dam, at the south end of Lake Havasu, but so far have not caused any major problems, said Bureau of Reclamation spokesperson Robert Walsh. "There are definitely quagga mussels at Parker Dam, but it is important to note that they are not affecting the plant's water release or power generating operation," Walsh wrote in an e-mail.
Last November, the Bureau hired an outside consultant to study the quagga mussel problem at Parker, Davis and Hoover dams. "That assessment indicated that the quantity of mussels and their apparent rate of growth is much greater at Parker Dam than at either Davis or Hoover dams," Welsh wrote.
The study noted that the water supply intakes on the face of the dam were at risk of mussel settlement and growth, as well as other exterior and interior equipment.
The quagga mussels - a close relative to the zebra mussel - spread with such great rapidity due to their unique reproductive system. Unlike native mussels, which depend on an intermediate host species to achieve reproduction, the zebra and quagga mussels simply release their gametes into the water to breed. "They're prolific, and they have this host-independent reproduction system, and that makes them very effective," de Leon said.
California's Fish and Game Department has launched an aggressive effort to prevent the further spread of the mussels into the state. Since being detected in the Colorado River Aqueduct system, which serves 26 municipalities in southern California, the quagga has spread to at least five reservoirs and several other lakes in California. "Any water body or water system that receives raw Colorado River water has been contaminated with the quagga," said Alexia Retallack, spokesperson for California Fish and Game.
Over the last year, border protection stations run by the California Department of Food and Agriculture have checked 82,964 boats entering the state. The purpose of the checks is to ensure that boats have been properly drained of water before they enter California, and that no mussels have attached themselves to parts of the boat.
The mussels can survive between three to five days out of water, during the summer, depending on the temperature, and as long as 30 days out of water in the winter.
So far the checks have netted 104 boats contaminated with quagga mussels or their larvae, which feel like sandpaper on smooth surfaces.
Biologist recommend completely draining all boat parts that can hold water, including bilges, live wells and motors, and waiting five days between visits to separate lakes.
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