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Drought And Floods Taxing California's Water System

Amy Quinton / Capital Public Radio

Buckle along the Delta-Mendota Canal in the Central Valley caused by subsidence in 2013. The canal is a major artery of the federal Central Valley Project.

Amy Quinton / Capital Public Radio

Both drought and floodwaters are testing California’s aging water infrastructure. 

A new NASA analysis shows too much groundwater pumping during the drought has caused the California Aqueduct to sink more than two feet near Avenal in Kings County.

It's reducing the amount of water that can be sent to Southern California. The Aqueduct is part of the State Water Project and supplies 25 million Californians and irrigates 1 million acres of farmland.  

As a result of the sinking, the Aqueduct can carry a flow of only 6,650 cubic feet per second, which is about 20 percent less that it was designed to carry. 

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“Our ability to move water may be compromised if the allocations of the State Water Project go beyond 85 percent," says Jeanine Jones with the California Department of Water Resources.

"Similarly, there are concerns on the flood control side as well, particularly in the reach of the San Joaquin River by the Eastside Bypass where there has been considerable subsidence.”

The report shows subsidence bowls are growing wider and deeper across hundreds of square miles. Land near Corcoran has subsided 22 inches, damaging the Delta-Mendota Canal, a major artery of the federal Central Valley Project.

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Another subsidence bowl is now 65 miles in diameter, and has deepened by 16 inches, damaging the Eastside flood bypass. Water managers say the land sink is on top of several feet of subsidence measured between 2008 and 2012.

The report also shows subsidence intensifying in a third area near Tranquility in Fresno County.

DWR says costs to repair the damage could be in the hundreds of millions of dollars. Thousands of groundwater wells near the system of canals and bypasses could be contributing to the subsidence. The department says it will consider legal actions to protect state infrastructure going forward.

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At the same time, state engineers are busy assessing a 250-foot long hole in Oroville dam’s spillway. The dam is the state's second largest and also part of the State Water Project.

“These are clearly problems that we have to address,” says Jay Lund, director of the UC Davis Center for Watershed Sciences.

“Certainly for the Oroville spillway, this is a clear public safety issue. If you don’t address these problems, it’s harder to keep people alive during major floods and we’re fortunate that this particular flood isn’t so bad just yet.”

Both the Oroville Dam and the California Aqueduct were built in the 1960s.