California’s Water System Built for a Climate We No Longer Have

Crews repair a weakened levee on Tyler Island in California's Delta.

Crews repair a weakened levee on Tyler Island in California's Delta. (Lauren Sommer/KQED)

Many Californians are still in disbelief that after five years of too little water during the drought, now the problem is too much water.

Heavy winter storms have done more than cause problems at Oroville Dam, where thousands of people were evacuated after erosion of a critical spillway. They’ve also stressed thousands of miles of levees and flood infrastructure downstream of the major dams.

Some say it’s a wake-up call because the state’s warming climate could mean more of the same.

Downstream Stress

With rivers running high, levee patrols have been on high alert for any sign of damage. Earlier this month, 60 feet of levee collapsed on Tyler Island, near the town of Walnut Grove in the Sacramento-San Joaquin Delta.

A huge crane was brought in to dump rocks in the gash, in the hope of preventing the river from breaking through.

“Every hour we work, we’re safer,” said Mello, a farmer on the island who anxiously watched every rock load. “We’re not out of the woods yet by a long shot.”

Nearby farms and homes would be underwater without the levee, as the island sits 17 feet below sea level at its lowest point. Mello watched the levee disintegrate in just 15 minutes.

California’s ‘New Climate’

“This shouldn’t be a surprise,” says Noah Diffenbaugh, climate scientist at Stanford University. “It’s actually exactly what’s been predicted by scientists for at least 30 years.”

California's backlog of levee maintenance runs hundreds of millions of dollars.
California’s backlog of levee maintenance runs hundreds of millions of dollars. (Lauren Sommer/KQED)

Diffenbaugh says while drought and floods aren’t new for California, climate change could make them both more extreme.

“If it’s hot out, water is going to evaporate,” said Diffenbaugh. “And that’s what happens with soils. We’re getting more frequent occurrences of low precipitation leading to drought because the temperatures are higher.”

During wet years, warmer temperatures will cause more precipitation to fall as rain instead of snow. The snowpack is also showing signs of melting earlier.

On the contrary, California’s water system was designed a century ago, around having a predictable snowpack in the Sierra Nevada, which acts like frozen reservoir, storing water until the spring.

California’s flood system can handle that slow melt, but isn’t really equipped for a huge amount of runoff all at once, Diffenbaugh says.

“Our water system was really built in an old climate,” he says. “It’s a climate that is no longer the climate of California.”

Updating Infrastructure

As California’s dams have struggled to handle the influx of winter rain, some are calling for more water storage projects to be built.

“Clearly our water model isn’t working,” reads a recent editorial in the Modesto Bee. “We need more dams.”

But even if dams are big enough to capture flood events, the channels below the dams may not be able to handle higher flows.

The spillway on Don Pedro Dam near Modesto was opened recently for the first time in 20 years, to prevent the reservoir from overflowing. But the amount of water operators could release has been limited by the capacity of the river channel below it.

A dredge drops rock on Tyler Island.
A dredge drops rock on the Tyler Island levee. (Lauren Sommer/KQED)

“This flood here has really tested us,” said Jay Lund, director of the Center for Watershed Sciences at UC Davis. “We’ve found we have quite a bit of levees to work on.”

Dams also aren’t the only option for storing water.

“The biggest source of water storage in California is groundwater and it always will be,” says Lund.

California has been experimenting with diverting floodwater onto fields, where it can seep into aquifers that were drawn down dramatically during the recent drought. That could potentially allow reservoirs to leave more room in the winter to catch extreme runoff events.

“If we’re able to move some of the storage to aquifers,” says Lund, “that should free up more storage in the reservoirs to capture that now bigger annual cycle of wet months.”.

The challenge for improving California’s flood readiness has long been funding.

The state has identified billions of dollars of flood control projects and levee maintenance that’s needed, as part of its Central Valley Flood Protection Plan.

“One of the big holes in our water system is that we don’t have very good regular funding for flood control,” notes Lund.

On Friday, Gov. Jerry Brown announced plans to spend $437 million on improving flood infrastructure, with money from a combination of sources, including federal dollars and Proposition 1, which California voters passed in 2014.

California’s Water System Built for a Climate We No Longer Have 24 February,2017Lauren Sommer
  • Hillary Clintub

    So is California going to trash their old water system and build a whole new one based on the climate they think they’re GOING to have? That seems like a pretty big casino bet for California’s taxpayers to have to back IMO. But I’m sure California’s politicians will assure them they know precisely what the future is going to be.

  • Jerry Duncan

    Pure false news. We have had problems because none of the infrastructure was maintained. That too has been a warning for many years.

    • Greg Nestor

      Spent all your money on feel good programs not what the state needed and protecting illegal Mexicans illegal Chinese

  • Colleen Cabot

    Another key focus in our urban areas is to require water retention landscaping: french drains within our yards, small retention ponding areas to slow down runoff, both to catch runoff from our rooves and driveways. Strategies like this, on residential and commercial properties, would help recharge our ground water.

    • Greg Nestor

      How about if the government quit geoengineering your atmosphere and stopping the rain from falling all then maybe you would have some rain and water in your aquifer

  • WaterGeek

    It’s kind of hilarious watching climate “scientists” trying to rewrite history to suggest that it’s somehow a “new” phenomenon that the California drought ended with a flood, especially since that’s been the typical pattern over time. Droughts almost always end with floods, see Texas and Australia for recent examples, but history is full of others if anyone cares to actually check instead of listening to bogus climate experts.

    • freedom1mac

      I feel the same way you do. There is nothing new under the sun! These scientists are full of it! Wouldn’t doubt that he was paid for by Jerry Brown.

      • Greg Nestor

        Probably used your tax dollars to do it to

    • Greg Nestor


    • Scott

      Not that ending the drought with a wet year is “new”, but that this drought was truly record setting, and we can expect those kinds of droughts to happen more often.

      But even if they were wrong, we’ve got serious water problems. We’ve built no new water storage since the 1970s, when the population of the state was 20 million. It’s now close to twice that. So, every dry year taxes our storage capacity more than it was designed for.


Lauren Sommer

Lauren is a radio reporter covering environment, water, and energy for KQED Science. As part of her day job, she has scaled Sierra Nevada peaks, run from charging elephant seals, and desperately tried to get her sea legs - all in pursuit of good radio. Her work has appeared on Marketplace, Living on Earth, Science Friday and NPR's Morning Edition and All Things Considered. You can find her on Twitter at @lesommer.

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