California’s Katrina Is Coming

Dennis Baldocchi, a biogeochemist at the University of California, walks on Sherman Island pasture, along some of the seepage from the Sacramento-San Joaquin River Delta, in November 2009.

 Dennis Baldocchi, a biogeochemist at the University of California, walks on Sherman Island pasture, along some of the seepage from the Sacramento-San Joaquin River Delta, in November 2009. TONY AVELAR/THE CHRISTIAN SCIENCE MONITOR/GETTY IMAGES


The summer dream has become a nightmare drought. But the years-long dry spell isn’t what keeps engineers, economists, and state water planners awake at night. No, they worry about the network of levees at the crux of California’s plumbing—a massive freshwater confluence called the Sacramento-San Joaquin River Delta.

Most of the state’s water is drawn from the Delta, protected by levees that pretty much amount to mounds of dirt, even when compared to infrastructure that infamously failed New Orleans during Hurricane Katrina. Hurricanes don’t hit NorCal, but these levees are alarmingly susceptible to disaster. If enough were to breach—in an earthquake perhaps, or severe El Niño storm—sea water from San Francisco Bay could rush in, tainting the water supply serving two-thirds of the state. The worst-case scenario could cause up to three years of severely curtailed water for most Californians.

Even if you’re not a California dreamer, this affects you. Delta water keeps Hollywood in the movie business, Silicon Valley in the tech business, and 750,000 acres of farmland in the business of producing half of America’s veggies, fruits, and nuts. If the levees go, so goes the water for 25 million residents of the world’s seventh largest economy.

The Delta is a singular place, even in California’s varied geography. Most of California’s interior water flows into two river systems—the Sacramento from the north, and the San Joaquin from the south. Where they meet, just east of the San Francisco Bay, they form a muggy tidal marsh with more than 70 inhabited islands. Most of these islands sit below sea level, due to groundwater pumping and natural compaction, and are ringed by tall, earthen levees. “An island in the Delta is really a bowl surrounded by a levee,” says Dave Mraz, chief levee engineer for the state Department of Water Resources. “If that levee goes, then that bowl is filled with water.”

Since 1900, over 160 levees have breached in the Delta. Several breached islands were never reclaimed, and nowexist only as levee-top lagoons.

leveefailuresClick to Open Overlay Gallery

People live, work, and farm in these island bowls, so any breach could have grave human and economic costs. But the levees also play a critical role in protecting the state’s water supply.

In the 1960s, California built two huge pumping stations at the southwest end of the Delta, about 50 miles east of San Francisco as the crow flies. They are the faucets for the State Water Project, which delivers Northern California water down 444 miles of aqueduct to Southern California. Through the pumps, the Delta provides municipal water to cities and towns from San Jose to San Diego. And it is the lifeline for a lot of the state’s agriculture industry. Those pumps are among the most important pieces of public property in California.

Every drop of water that passes through those those pumps first passes between many miles of levees. If a levee breaches, water rushes in. If enough levees breach on enough islands—or on a large enough island—the volume of fresh water in the Delta is insufficient to fill the void that was once an island. That brings in water from the Bay. Salty, Pacific Ocean water. “If you have ten or 15 levee failures and a big slug of salt water comes in, the salinity goes way up and you have to shut down the pumps,” says Mraz. Engineers call this scenario the Big Gulp.

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