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Major earthquake in the Delta could be disastrous for California's water supply

California's water supply at risk in event of a major earthquake near the Delta
California's water supply at risk in event of a major earthquake near the Delta 03:52

ISLETON -- While the earthquake that struck near Isleton Wednesday morning wasn't strong, the location did raise questions about the possible risk to an area that is critical to the state's water supply. 

The Delta region in Sacramento County relies on more than 1,000 miles of aging levees to protect local farms and communities that could be vulnerable in a more powerful quake.

Nothing shattered at Isleton's Delta Boyz Dispensary, but the aging structure it is housed in got a good shake. Cameras caught the staff jumping out of their seats just before 9:30 a.m.

"Yeah. This is an old building. It's been here for a long time. Isleton was erected I guess 120, 130 years ago," said Vince Perdue, who works at Delta Boyz Dispensary. "You've even got the security guard up top. He even got up and came in. It was a trip, for sure. Definitely doesn't happen out here very often. At least not as long as I've been here."

At the very center of California's water system, so much of what we can use comes from or through the Delta. The Delta itself depends on levees to contain the water.  All of that could be compromised if the earthquake is strong enough.  

"A very large earthquake, centered near the Delta, would pose a particularly significant threat to both protective systems that the levees provide, as well as the water distribution and intake systems," explained Austin Elliott with the USGS. 

A large enough failure would mean massive interruptions to California water systems, with large scale repairs needed before things were working again. Wednesday morning's relatively mild Delta quake provided both an unexpected jolt and a serious reminder.

"We are fortunate that the earthquake today was just a magnitude 4.2," said Elliott. "Larger earthquakes magnitude -- five or six -- would begin to produce liquefaction and damage some of the infrastructure and geotechnical work there." 

Another possible factor to consider is the timing of a potentially damaging earthquake of higher magnitude. In mid-October, water levels were considerably lower than they had been during the spring and summer when runoff from the Sierra had rivers absolutely at capacity with water. 

If a significant earthquake struck when the Delta was completely swollen with water, the stakes would obviously be much higher. 

"It's a sort of a trial run," added Elliot. "A reminder for our infrastructure systems that they are eventually going to have to confront a pretty significant earthquake hazard."

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