State releases water from its filling reservoirs

As a wet winter continues to fill California reservoirs, water managers set their sights on flood prevention Thursday and today by releasing water from stockpiles to make room for approaching storms and melting snow from the Sierra Nevada.

With the warm atmospheric rivers expected to cause local flooding, the looming question is whether warm rains will melt much of the near-record snowpack and bloat the state’s rivers over coming weeks.

Reservoir operators typically aim to keep water levels high ahead of summer months, but the race to make room for additional water underscores how weather extremes are making management of the state’s water infrastructure increasingly challenging.

“Water management in California is complicated and it’s been made even more complex with these challenging climate conditions, where we see swings between very dry and very wet then back to dry and now we’re back to wet,” said Ryan Endean, a spokesperson at the Department of Water Resources in a news briefing Thursday.

With the series of atmospheric rivers expected to make landfall late Thursday and through the weekend, flood management officials highlighted risk from river tributaries in the Sacramento and San Joaquin Valleys as well as along the Central Coast. Gov. Gavin Newsom issued an emergency proclamation in 34 counties.

Bureau of Reclamation staff said over the next few days they are releasing water in increasing intervals for two days from Folsom Dam into the American River for flood protection in the Sacramento region, as well as from Friant and Shasta dams.

The Department of Water Resources also said they are releasing a relatively small amount water from the reconstructed spillway at Oroville Dam, which has had few opportunities to test the channel after a 2017 storm caused severe damage and prompted the evacuation of over 100,000 people.

“The reconstruction included two and a half feet thick of concrete over another five foot thick section,” said Ted Craddock, deputy director of the State Water Project. “It’s a very robust structure that was reviewed by independent experts as part of the design and construction, so we’re confident in its ability to pass flood flows.”

In this wet winter with near-record snowpack, the state’s eight largest reservoirs have seen their water levels steadily rise since December. Three of the major reservoirs, Oroville, Don Pedro and McClure, surpassed their historical averages for this time of year.

All the water is a welcome reprieve for farms and cities that can expect water deliveries from the state’s network of reservoirs, rivers and aqueducts. Operators of the State Water Project and Central Valley Project, the plumbing that delivers water across the state, expect to allocate significantly more water to agricultural districts, towns and cities this year.

But long term, climate projections for drier dry spells and wetter wet periods are making California water management increasingly challenging, say Public Policy Institute of California researchers. Water decisions are typically based on historical average forecasts, which are increasingly unhelpful.

Rain and snowfall this winter have made a significant dent in California’s three-year drought, which state scientists characterized as the driest period in a century. Just 19% of the state is experiencing “severe drought,” down from 40% in September, but scientists are quick to note a single wet season can’t replenish the state’s overdrafted groundwater basins.

“I think for many purposes, this particular drought is going to be over,” said Jay Lund, codirector of the UC Davis Center for Watershed Sciences. “We’ll still have some legacy of this drought in terms of low groundwater levels in some parts of the state, and maybe a very long or permanent legacy of forest health and aquatic ecosystems.”

In addition to water storage, deliveries, and flood management, reservoir operators are also responsible for counteracting harmful effects that dams have on river and wetland ecosystems. Many environmentalists say that priority fell to the wayside this year after Gov. Gavin Newsom waived environmental rules in February to preserve water in reservoirs for farms and cities down south.

“You intervened and cut environmental protections for fish and wildlife to do a water transfer from the environment to large landowners in the San Joaquin Valley and look what it got you,” said Jon Rosenfield, pointing to the populations of near-extinct native fish that could have benefited. “You have to dump that water anyway.”

But Scott Petersen, director of water policy for the San Luis & Delta-Mendota Water Authority, a group of agricultural water districts with federal water contracts south of the Delta, defended the governor’s decision. He said the antiquated environmental rules were made for a more predictable climate that no longer exists.

“It can’t be a hindsight question,” he said. “If you’re trying to move to more real time management of the system, which you have to in an era of a rapidly changing climate, then that decision has to be viewed in the context of the information you had at the time.”