Oct. 1 is the beginning of what hydrologists call the “water year.”

Historically, California’s reservoirs are near their lowest levels by this point after months of being drawn down, mostly to irrigate fields and orchards, during the state’s precipitation-free summer.

This October is quite different.

Last winter’s heavy rain and snow storms, generated by a series of atmospheric rivers, filled reservoirs even as dam managers fully opened their gates to send as much water downstream as possible.

So much rain and snow fell in the southern San Joaquin Valley that Tulare Lake, once one of the nation’s largest natural lakes, was recreated, and threatened the town of Corcoran.

Virtually every reservoir in the state contains more than 100% of their historic storage levels at the beginning of the water year. The biggest ones, such as Shasta and Oroville, are close to three-quarters full even after giving farmers their full quotas of irrigation water during the growing season.

Hydrologists and meteorologists, moreover, are telling Californians that they may see a repeat in the months ahead, thanks to a phenomenon known as El Niño, and it potentially could surpass last winter’s storms.

El Niño is a warm current that often results in huge amounts of Pacific Ocean water being sucked into the atmosphere and delivered to land as rain and snow.

“The anticipated strong El Niño is the predominant climate factor driving the U.S. winter outlook this year,” Jon Gottschalck, chief of the operational prediction branch at NOAA’s Climate Prediction Center, told the Los Angeles Times.

El Niño Could Bring Historic Rainfall

He and other weather scientists predict that California and other Western states will see above-average precipitation and some believe it could surpass the 1997-98 winter when floods and mudslides killed 17 Californians and caused $1 billion in property damage.

“It’s only been seen three times previously in the historical record,” Stephen Yeager, project scientist with the National Center for Atmospheric Research, told public radio station KQED. “We are looking at the potential of a major season-long event that could impact people and their livelihoods.

The prospect of another heavy precipitation winter is both uplifting to a state that had experienced several years of drought prior to last winter and a little frightening.

Mostly, it’s another warning to Californians – and particularly their politicians – that it’s beyond time to take the state’s water situation seriously and become more proactive on both flood protection and water storage.

The good news is that after years of dithering, some significant progress is being made on rationalizing water management in California. A few days ago, federal and local water officials announced the approval of a project that would expand storage in the San Luis Reservoir, a major off-stream facility in the Pacheco Pass.

San Luis absorbs water from the California Aqueduct that’s not currently needed and releases it on demand. It has the capacity to store 2 million acre-feet now and the new project will add another 130,000 acre-feet of capacity.

It’s one out of a flurry of storage projects now in the works, including another off-stream reservoir on the west side of the Sacramento Valley called Sites. That project has been kicking around for decades and is finally gaining political approval and serious commitments of money.

Off-stream storage avoids the environmental issues of dams that plug rivers, such as Shasta and Oroville, and adversely affect fish and other wildlife.

State water authorities believe that, with climate change, California will receive more of its precipitation as rain, rather than snow. It’s critical, therefore, that we have storage, both above-ground and in aquifers, to replace the natural reservoir of the Sierra snowpack as it recedes.

The message is finally hitting home.

About the Author

Dan Walters has been a journalist for nearly 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. CalMatters is a public interest journalism venture committed to explaining how California’s state Capitol works and why it matters. For more columns by Dan Walters, go to calmatters.org/commentary.

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