The federal government sued California on Thursday over a water policy it said violates the state's environmental protection law.
The U.S. Department of Justice filed suit in Sacramento federal court to block a contentious plan approved in December to increase river flows in the San Joaquin River and three tributaries to help revive dwindling salmon populations.
It was part of a larger effort to protect the Sacramento-San Joaquin River Delta, which state officials called an "ecosystem in crisis." The delta supplies water for the majority of California's people and farms.
Once-thriving fish in the delta, which flows out to San Francisco Bay, have plunged from some 70,000 adult Chinook salmon returning to the San Joaquin basin in the fall of 1984 to just 10,000 in 2017.