Opinion | Climate change increases uncertainty of CA water supply - CalMatters

Opinion | Climate change increases uncertainty of CA water supply
Stone Corral Creek, shown here on on Feb. 14, 2023, will be about 200 feet underwater when the Sites Reservoir is built in the western Sacramento Valley. Photo by Julie A. Hotz for CalMatters

In summary

As California’s precipitation becomes more erratic due to climate change, the state needs more tools, including more storage capacity, to make the water supply reliable.

There’s no issue more important to California than having a reliable supply of water, but the situation is increasingly uncertain from both immediate and long-term perspectives.

Last week, federal and state water regulators told the state’s municipal water agencies and San Joaquin Valley farmers that they could count on getting just 15% of their contracted allocations this year because precipitation this winter in Northern California has fallen short of normal, despite storms that caused serious flooding in Southern California.

“Many expected the initial allocation to be higher,” Federico Barajas, executive director of the San Luis & Delta-Mendota Water Authority, which represents dozens of agencies that receive Central Valley Project water, told the San Francisco Chronicle. “This low initial allocation is particularly challenging for agricultural producers, who are reliant on these projections for planning crops to grow during the year and for acquiring the financing necessary to support food production.”

However, as reservoir managers were issuing that grim projection, they were also drawing down reservoir levels, which had soared from last winter’s heavy storms, to create space for anticipated runoffs later in the spring.

California has historically received most of its precipitation during a few winter months while the remainder of the year is dry. It’s why federal, state local agencies have constructed dozens of dams and reservoirs to collect water when it is available for delivery to users during drier periods.

However, the peaks of precipitation appear to be getting higher – witness this year’s near-hurricanes in Southern California – and the periods of drought seem to be becoming longer due to climate change. They upset the models that water managers have traditionally used to decide when to boost reservoir storage and when to increase releases.

Another big storm is expected later this week, and it could dump enough snow in the Sierra to bring the snowpack up to normal levels and eventually increase allocations to water users, but that’s speculation. Meanwhile, with the spring planting season approaching, farmers must guess how much water they will have to irrigate their crops.

However, we need more storage options, both surface and underground, and we need to resolve some knotty issues, such as the decades-long controversy over a tunnel or some other conveyance to bypass the Sacramento-San Joaquin Delta so that more Sacramento River water can be sent southward for use or storage.

That project, meanwhile, is politically tied to efforts by the state to either persuade farmers on the San Joaquin River to reduce their diversions so that more water can flow through the Delta to enhance wildlife habitat, or force reductions by issuing new water quality standards for the Delta.

As the supply picture becomes less certain, California cannot afford more decades of gridlock and squabbling.

Dan Walters has been a journalist for more than 60 years, spending all but a few of those years working for California newspapers. He began his professional career in 1960, at age 16, at the Humboldt Times... More by Dan Walters