A projected increase in the kind of “atmospheric river” type storms California experienced in the historic 2023 water year could be disastrous for the San Joaquin Valley – or its salvation.

Monserrat Solis

California Local News Fellow

SJV Water

The difference depends on whether locals can adapt to the coming changes by absorbing the intermittent deluges and storing that water for later dry times.

Right now, systems in the San Joaquin and Sacramento River watersheds were built to collect and move precipitation that first lands as snow in the Sierra Nevada mountains and then slowly melts through springtime.

A warmer climate, though, will mean more rain than snow, filling rivers and reservoirs more quickly, said Daniel Swain, a climate scientist at the Institute of the Environment and Sustainability at UCLA, during a webinar hosted by the Sustainable Conservation.

“This is particularly true in the San Joaquin and Sacramento River watersheds,” he said.

In 2023, that scenario played out in flooded homes, businesses and cropland causing millions in damage. Swain said a “flood bypass system” could protect populated areas and recharge overpumpted aquifers.

He sketched out a system that would include levees, expanded natural flood plains along rivers and more catch basins to handle floodwater.

Such a system would “…also potentially makes water managers a little less concerned about releasing water from dams ahead of storms, because then you can release water further in advance, give yourself a better dam safety margin if there’s a really big flood event, but in the form of underground aquifers rather than in the dam,” Swain explained.

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Lessons from the 2023 Floods

The 2023 floods showed in real time how important that preparation can be.

On the Kern River, for example, downstream water managers have spent 30 years building recharge basins. That vast available acreage soaked up more than 1.3 million acre feet of flood water. It also allowed water managers to work with the Army Corps of Engineers, which owns and operates Isabella Dam, to time releases so homes and infrastructure weren’t damaged.

Ultimately, only 24,000 acre feet of Kern River water overflowed local capacity and had to be released into the California Aqueduct.

Back in 1983, very similar to the 2023 water year, more than 425,000 acre feet flooded out of the Kern River into the aqueduct and north into the old Tulare Lake bed, adding to severe flooding in that region.

On the Kings River in 2023, runoff was 4.5 million acre feet compared to its average of 1.7 million acre feet, according to Kings River Watermaster Steve Haugen.

The Kings, along with the Tule and Kaweah rivers, as well as numerous smaller streams, flooded the old Tulare Lake bed, wreaking havoc on farms and dairies and flooding homes. The Tulare Lake bed is heavily silted and doesn’t percolate water into the aquifer very effectively, which meant farmers had to pump water off the lake bed.

Haugen said about 1 million acre feet of 2023 flood water was moved to recharge basins.

Twitter screengrab of satellite mapping showing water covering the northern and southeastern sections of Tulare Lake in 2023.

Local water districts in Kings and Tulare counties are busy building more recharge basins, but a bypass system as outlined by Swain would be hugely expensive, Haugen said.

He estimated buying land, building levees and canals and completing an environmental impact report under the California Environmental Quality Act (CEQA) could cost $100 million. And that wouldn’t include managing and maintaining the system.

The existing system, though not a bypass system envisioned by Swain, “…is set up to function in a fashion similar,” Haugen said.

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Challenges and Opportunities for Flood Management

Swain also advocated restoring natural flood plains along Central Valley rivers and streams. Unlike major cities such as Los Angeles where apartment buildings are right next to the Los Angeles River, the Central Valley has more open spaces.

“There is a little bit of an opportunity in the San Joaquin Valley in that respect, because it’s not empty land, but it’s also not highly populated cities in a lot of the places that could potentially be the sites for floodplain restoration,” Swain said.

He acknowledged such a bypass system comes with significant challenges including:

• Acquiring land – though with more pressure to reduce groundwater use per the Sustainable Groundwater Management Act, up to 1 million acres of farmland may have to be fallowed
• Cost to build and maintain
• Impacts to small farmers
• Environmental impact
• And, perhaps most of all, politics

“Everything with California water is complicated and fraught, politically, financially, legally, there’s so many complicating factors that make it very difficult to do new and innovative things in general,” Swain said.

About the Author

Monserrat Solis covers Kings County water issues for SJV Water through the California Local News Fellowship initiative.

About SJV Water

SJV Water is an independent, nonprofit news site covering water in the San Joaquin Valley, www.sjvwater.org. Email us at sjvwater@sjvwater.org.