L.A. Looks to Protect Water Sources from San Andreas Earthquake

L.A. Looks to Protect Water Sources from San Andreas Earthquake

Los Angeles Mayor Eric Garcetti has ordered the city’s three main water agencies to draft proposals for protecting the Southland’s vulnerable aqueducts in the event of a catastrophic earthquake along the San Andreas fault.

Los Angeles gets nearly 90 percent of its water from three main aqueducts, according to the Los Angeles Times. The city’s main sources of water are the Colorado River, the Owens Valley, and the Sacramento-San Joaquin River Delta, whose water moves through the Colorado River Aqueduct, the Los Angeles Aqueduct, and the Edmund G. Brown California Aqueduct, respectively.

However, the water and the aqueducts that transport it cross the notorious San Andreas fault line 32 times. Water officials have warned that a significant earthquake along the San Andreas fault could collapse one or more of the aqueducts, imperiling the water supply for millions in Southern California.

“We’re the first city that’s really bet its life on outside water,” U.S. Geological Survey seismologist Lucy Jones told the Times. “We have to cross the faults. There’s no way to not go over the fault.”

Mayor Garcetti has asked the city’s three main water agencies, the Department of Water and Power (DWP), the Department of Water Resources (DWR), and the Metropolitan Water District of Southern California to come up with a plan by July. Specifically, Garcetti wants the proposals to include a plan for strengthening the Los Angeles Aqueduct and a plan for a bond measure that would fund water-related earthquake safety projects. The mayor also wants to know which of Los Angeles’ more than 100-year-old pipes needs to be replaced first.

Garcetti told the Times that water is “one of L.A.’s greatest earthquake vulnerabilities,” and that while the cost of protecting the city’s water supply from seismic activity is likely to be in the billions, the economic and human cost of the damaged or destroyed aqueducts would be far worse.

“If it were to take six months to get our water system back… residents and businesses would be forced to relocate for so long that they might never come back,” Garcetti told the paper.

None of the aqueducts have yet been involved in a large-scale earthquake on the San Andreas fault. The last massive temblor on the fault occurred in 1857, when a magnitude-7.9 quake struck. All three aqueducts were constructed in the 20th century.

The Department of Water and Power is reportedly already working on a temporary solution for the Los Angeles Aqueduct; namely, placing a durable, 3-foot wide plastic pipe through the Elizabeth Tunnel under the mountains near Santa Clarita, where the aqueduct crosses the San Andreas fault. DWP officials hope that even if the aqueduct were to collapse, the plastic pipe could preserve a small window for water to get through.

Colorado River and California Aqueduct officials told the Times they are studying the earthquake-related vulnerabilities of the systems.

While Los Angeles’s water agencies determine the best course of action to protect the Southland’s water supply from earthquakes, the city may at least be better aware of when exactly that earthquake will hit; the recent Senate-approved $1.1 trillion spending bill includes $5 million for the implementation of an early warning earthquake system in the Golden State. Working correctly, the system could give Californians up to 60 seconds of warning before an earthquake strikes.