California Quake Could Devastate Water Supply
SACRAMENTO — A major Northern California earthquake could severely damage the Sacramento-San Joaquin Delta levee system and jeopardize the water supply for two-thirds of Californians for more than a year, a top state water official warned Tuesday.
Last year, the unexplained collapse of a single levee shut water pumping for days and cost $100 million to repair. An earthquake could lead to the collapse of many sections of levees, which channel Northern California rivers on their run to San Francisco Bay, said Lester Snow, director of the California Department of Water Resources
“This is not a worst-case scenario,” he said. “We think it’s a plausible scenario of what could happen in the delta.”
Snow told a joint hearing of three state Senate committees that a 6.5-magnitude earthquake could collapse 30 levees, flood 16 delta islands and damage 200 miles of additional levees. Some 3,000 homes and 85,000 acres of farmland would be flooded.
The ruptured levees also would allow salt water to rush in to the river system, causing an immediate shutdown of the pumps that send water south to San Joaquin Valley farmers and Southern California water districts. Cities would have to use alternative water sources and resort to rationing, Snow said.
Three state highways and railroad tracks would be submerged, and petroleum and natural gas pipelines would have to be shut down. Damage could reach $30 billion over five years, Snow said.
It would cost $1.3 billion to strengthen 500 miles of delta levees so they are not subject to erosion in a flood, but even that would do nothing to make them more resistant to earthquakes, said Leslie F. Harder Jr., the water resources department’s acting deputy director for public safety.
Among the possible long-term fixes are flooding some islands that are surrounded by levees. Flooding would equalize water pressure on the islands, making a levee collapse less likely.
Despite the warnings, no delta levee has collapsed because of an earthquake, said Thomas Zuckerman, general manager and co-counsel of the Central Delta Water Agency. He said strengthening levees around just three islands at the mouth of the delta could reduce 70 percent of the risk.
Lawmakers said there is not enough money for significant levee improvements. State tax bonds would be needed to make the necessary repairs, said state senators Michael Machado, D-Linden, and Tom Torlakson, D-Antioch.
On the Net:
See the Department of Water Resources’ earthquake presentation at http://www.water.ca.gov