California’s Hydrological Prospects: Filling Reservoirs and the Looming El Niño

The commencement of October marks the beginning of what hydrologists refer to as the “water year” in California. Historically, this period witnessed the state’s reservoirs at their lowest levels after months of water consumption, mainly for irrigation during the precipitation-free summer months. However, this year, the situation is strikingly different.

Last winter, California experienced heavy rain and snowfall generated by a series of atmospheric rivers. These storms, combined with diligent dam management, resulted in reservoirs filling up. In fact, so much water fell in the southern San Joaquin Valley that Tulare Lake, once one of the nation’s largest natural lakes, was reestablished, even posing a threat to the town of Corcoran.

As we enter the water year, nearly every reservoir in the state contains over 100% of its historical storage levels. Even the largest reservoirs, like Shasta and Oroville, are almost three-quarters full despite providing farmers with their full irrigation water quotas.

Hydrologists and meteorologists have more good news for Californians, suggesting that this trend may continue in the coming months due to a weather phenomenon known as El Niño. In essence, El Niño is a warm ocean current that draws moisture from the Pacific Ocean into the atmosphere and delivers it as rain and snow to land.

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

There’s a consensus among weather experts that California and other Western states can expect above-average precipitation. Some even believe it could surpass the powerful 1997-98 El Niño event, which brought deadly floods and mudslides.

This potential for a heavy precipitation winter is both uplifting and daunting for California. After several years of drought, the state is eager to replenish its water reserves but is also wary of the potential damage that excessive rainfall can cause.

The looming El Niño serves as yet another reminder for Californians, and their politicians in particular, to treat the state’s water situation with utmost seriousness. The time has come to take proactive measures, not only to bolster flood protection but also to enhance water storage.

Thankfully, the good news is that after years of delay and inaction, significant progress is being made in rationalizing water management in California. Recently, federal and local water officials approved a project that will expand storage in the San Luis Reservoir, a crucial off-stream facility in the Pacheco Pass.

The San Luis Reservoir absorbs excess water from the California Aqueduct and releases it on demand. The new project will add 130,000 acre-feet of capacity to its existing 2 million acre-feet, making it a substantial water storage resource.

This is just one of several storage projects in the works, including another off-stream reservoir called Sites on the west side of the Sacramento Valley. This particular project, which has been under consideration for decades, is now gaining political approval and financial commitments.

These off-stream storage solutions offer advantages over traditional dams that obstruct rivers and harm aquatic life. State water authorities are increasingly aware that as climate change progresses, California will receive more of its precipitation as rain rather than snow. Thus, the need for above-ground and aquifer storage is growing in importance, particularly as the natural reservoir of the Sierra snowpack recedes.

The message is clear and seems to be taking hold – it’s high time for California to invest in water infrastructure, and both state and federal entities are finally on the right track to secure the state’s water future.

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