Plummeting reservoir levels could soon force Oroville hydropower offline

A major California hydroelectric power plant could soon stop generating power amid worsening drought conditions.

According to state water officials, the Edward Hyatt Powerplant at Lake Oroville could go offline as soon as August or September — a time frame that would coincide with a feared power crunch this summer. The plant, which opened in the late 1960s, has never been forced offline by low lake levels before.

“I think it’s a bit shocking,” said Jordan Kern, a professor at the department of forestry and environmental resources at North Carolina State University. “The fact that it’s projected to go offline just speaks to how severe the drought is,” said Kern, who studies how power grids are impacted by extreme weather.

California Energy Commission spokesperson Lindsay Buckley said the commission is actively planning for the power plant to go offline this summer. But the Hyatt power plant is far from the only hydroelectric power source in the state that will likely be affected by California’s extreme weather.

On July 1, the energy commission, along with the California Independent System Operator and the California Public Utilities Commission, released a letter touching on the drought-driven hydropower losses expected this year, which are occurring amid historic heat event driven by climate change. According to the system operator, drought conditions could reduce the state’s hydropower capacity by up to approximately 1,000 megawatts in the coming months.

The Hyatt power plant is designed to produce up to 750 megawatts of power but typically produces between 100 and 400 megawatts, depending on lake levels. According to Buckley, average high demand in a day across the state is typically about 44,000 megawatts, so 400 megawatts would be a little less than 1% of that total.

“It’s not necessarily the tipping point,” Buckley said. “There’s a lot of different factors that are challenging overall grid reliability this summer. And Hyatt is one piece of the story.”

For decades, outflows from Lake Oroville — California’s second-largest reservoir — have generated electricity that feeds into the statewide grid. Located in the western foothills of the Sierra Nevada, the Oroville Dam complex includes the eponymous dam and three power plants that work together to pump and store water and generate hydroelectric power. The facilities also serve flood management, water quality improvement and fish and wildlife needs. The complex is a key component of the State Water Project, a 700-mile system of aqueducts, reservoirs and pumping plants that stores and distributes water to urban and agricultural users in Northern California, the San Francisco Bay Area, the San Joaquin Valley and Southern California.

Water from the Feather River, which is heavily impacted by precipitation and snowmelt, feeds into the Oroville complex. The dam releases water back into the Feather River, which goes downstream into the Sacramento River and eventually into the California Delta.

Like many things in California, recent travails at Lake Oroville have been a tale of extremes. In 2017, millions of gallons of water eroded the dam’s main and emergency spillways, forcing the evacuation of thousands of residents. The 2016-17 rain season was one of the wettest in California history, bringing more water to Lake Oroville than the reservoir could hold, which was one of several factors that led to the 2017 crisis.

Just four and a half years later, fortunes on the banks of the lake look vastly different. Aerial pictures of the reservoir — a key stockpile of California water supply and a popular recreation destination — have come to symbolize the current drought, with houseboats dwarfed by the steep banks and boat ramps that stop well above the water line. Lake Oroville is currently at 661 feet elevation with 982,000-acre feet of storage, which is 28% of its total capacity and 36% of its historical average, according to the California Department of Water Resources.

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“Hyatt Powerplant is not able to generate power once the lake elevation falls below approximately 630-640 feet due to lack of sufficient water to turn the plant’s hydropower turbines,” said John Yarbrough, assistant deputy director of the State Water Project at the California Department of Water Resource. “This would be the first time Hyatt has lost generation capabilities because of a low lake elevation,” he said in an emailed statement.

In 1977, during what was then California’s worst recorded drought, the power plant generated minimal electricity but stayed online. The power plant also stayed online during 2014 and 2015, during what is now considered to be the worst drought in state history.

But according to the California Department of Water Resources, Lake Oroville received only about 20% of expected runoff from the snowmelt this year, which the DWR characterized as a record low amount.

If the power plant does stop generating power, it will likely remain offline for months. “The resumption of power generation would be dependent on lake levels returning to elevations that allow us to operate the powerplant,” Yarbrough said.

One would need a crystal ball to give an exact date, but because the reservoir is fed by runoff from the Feather River, we could be well into November or early December before sufficient precipitation arrives in California to turn the underground turbines back on.

Additional energy to make up for the state’s reduced hydropower supplies this summer will come from other power sources, according to California ISO, the entity that oversees the flow of electric power throughout most of state. “It could come from several other dispatchable resources within the ISO, natural gas being the largest category of those, or any number of resource types outside the ISO that bid in as imports,” said California ISO spokesperson Anne Gonzales.

Broadly speaking, a drought affects the energy system in two main ways. There is less surface water, with less water flowing in streams and rivers and less electricity able to be generated from hydropower sources like the Hyatt power plant. Drier years also tend to be hotter years. That extreme heat not only compounds the drought, it also means demand for electricity can soar as millions of people turn up the air conditioning to stave off the heat.

“The overall message has been that climate change is impacting a number of our systems. Electricity is one of them. We’re asking consumers to be aware this summer,” Buckley said, urging Californians to sign up to receive Flex Alerts this summer so they can help conserve energy during moments of strain on the grid.