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Melting record snowpack could flood LA Aqueduct and Owens Valley

California snow depth on March 16, 2016 (left) and March 16, 2015 (right).
National Oceanic and Atmospheric Administration
California snow depth on March 16, 2016 (left) and March 16, 2015 (right).

The city of Los Angeles gets much of its water from the Owens River watershed in the Eastern Sierra Nevada. But the record snowpack there could produce more runoff this spring and summer than LA’s Department of Water and Power is able to handle, officials said Monday.   

That's why Mayor Eric Garcetti declared a local emergency Monday to authorize DWP to contract for equipment and experts to prevent flooding at Owens Lake and along the 200-plus miles of the Los Angeles Aqueduct. Highway 395 and downstream communities like Bishop and Independence are most vulnerable.

The emergency declaration takes immediate effect for seven days, after which it may be extended by a vote of the City Council.    

The Eastern Sierra snowpack, at about 241 percent of normal, will melt and is expected to dump as much as 1 million acre feet of into the aqueduct and the Owens dry lake bed about 200 miles north of Los Angeles. 
The city is planning to channel half that amount south along the aqueduct to DWP customers. That water windfall should enable the city to nearly halt its purchases of costlier water from the Metropolitan Water District. That should translate into lower water bills for Angelenos later this year.    

About 30 percent of the runoff is expected to be stored in underground aquifers, recharging groundwater supplies to a significant extent. But the remaining 20 percent of the melting snowpack, about 200,000 acre feet of water, could inundate Owens Lake, flooding the $1.1 billion in dust control measures the city has installed since 2000.
Construction of the L.A. Aqueduct  diverted so much of the lake's water to Los Angeles, it left behind a salty dry lake bed. Dust blowing off the lake made the Owens Valley one of the most polluted air basins in the nation. After decades of court battles pitting the city against Owens Valley plaintiffs, the LA DWP agreed to control the dust.

The mayor's declaration of emergency calls for digging channels to steer the water away from the dust-control projects, said Richard Harasick with LA DWP.

"The department has also taken emergency action to armor and repair certain Los Angeles Aqueduct facilities from floodwater impacts," Harasick said.
The utility expects to spend about $500 million responding to the surplus runoff. Much of the money could be diverted from new efforts to control dust and improve air quality for the Owens Valley. That money will instead be spent to protect what's been built and to prevent and respond to flooding along the aqueduct.