Mark Cowin: Levees alone won’t secure California’s water
Some people discount the risk of earthquakes in the Sacramento-San Joaquin River Delta.
They say building levees taller and wider will protect the region’s towns, farms, gas lines, highways and the water supply that serves 25 million Californians. They accuse the Department of Water Resources of exaggerating the need to shift the state’s major water project pumps from their current location along south Delta channels.
In fact, the department would be irresponsible to ignore the powerful forces threatening the Delta, its ecosystem and the water supplies that sustain much of the state’s economy.
In coming decades, the rising Pacific Ocean will push salty tides higher into the Delta from the west. Storms that fall increasingly as rain, not snow, will swell the rivers that empty to the Delta from the east. Squeezed in the middle are 1,100 miles of levees, earthen embankments that make farming possible in a low-lying region that was once marshland.
Faults cross the Delta and the nearby Bay Area. Experts put the chance of earthquake damage in the western Delta over the next 30 years at greater than 45 percent. Each year that passes uneventfully raises the risk, as fault stress builds.
Should multiple levees fail in the central Delta, where subsidence of peat soil puts additional pressure on levees, the bowllike islands there would flood, triggering an onrush of salty ocean water and the shutdown of the major pumps. Meanwhile, rising temperatures will further stress fish species, likely leading to even more stringentrestrictions on water supply to protect fish.
California has invested to keep key sections of Delta levees strong — $300 million since 2005 — and will continue to do so. But to rely solely on levees to safeguard a water supply critical to the state’s nearly $2 trillion economy would be negligent.
The state and federal governments, working with other groups, have forged a more durable solution called the Bay Delta Conservation Plan. It improves water supply reliability for much of the state and restores the region’s threatened fish species, while enhancing the cultural, agricultural and recreational values of the Delta. It features three main elements: creation of more than 100,000 acres of wildlife habitat; vigorous scientific assessment to gauge the recovery of threatened species and adjust accordingly; and the relocation of the Delta’s major water diversion point.
The plan builds new intakes on the Sacramento River and two tunnels to carry water 35 miles south to the pumping plants near Tracy. From there, water would flow into the aqueducts that supply the Silicon Valley, San Joaquin Valley and cities from Ventura to San Diego.
An underground system would be safe from natural disaster and would help fish, which would be shielded from the new intakes with modern screens more effective than those at the existing south Delta pumping plants. A northern diversion would allow for more natural east-to-west flows and richer fish food production. In addition, the plan eases water transfers between willing buyers and sellers, a critical way to cope with drought.
At a cost of $14 billion, this would not be cheap. But customers of the water districts that depend on Delta water would pay for it, not general taxpayers. If we invest now to secure the Delta ecosystem and water supplies, future generations will thank us.