HEMET, Calif. – Portions of the 242-mile Colorado River Aqueduct will be shut down starting Friday to fight the spread of an invasive mussel that can clog the system that helps supply water to an estimated 18 million people.

Sections of the aqueduct are to be closed for 10 days to kill young quagga mussels, a thumbnail-sized Ukrainian invader.

Hundreds of quaggas were found in the aqueduct during a maintenance shutdown in March. Inspections last month found the mussels had spread about 100 miles west.

Water in reservoirs will be used to make up the supply during the shutdown, said Bob Muir, a Metropolitan Water District spokesman.

Quaggas also have been spotted in lakes throughout Arizona, and the mollusks created a billion-dollar problem in the Great Lakes area by clogging water pipelines and altering ecosystems.

A service of the Associated Press(AP)