RIALTO, Calif.—The Rialto City Council has declared a state of emergency as it faces a dwindling water supply and the task of removing harmful chemicals from contaminating more water.

Officials declared the emergency Tuesday in hopes of receiving state funding to help clean up a six-mile-long plume of perchlorate that's moving through the city's drinking water supply from industrial sites.

Perchlorate is a chemical used in rocket fuel and defense equipment manufacturing.

"A chronic local condition has evolved into an acute emergency," city administrator Henry Garcia wrote in the declaration ratified by the council.

Officials said a regional drought and recently imposed limits on water imported from Northern California also prompted them to declare the emergency.

Rialto is about 60 miles east of Los Angeles.