The huge snowpack that has blanketed the Sierra Nevada this winter has done more than end California’s drought and extend ski season. It’s also changing how Californians keep the lights on.
With reservoirs full across the state, hydroelectricity generation from dams is expected to expand dramatically this summer, after three dry years when it was badly hobbled.
In 2017, a wet year similar to this one, hydropower made up 21% of all the electricity generated in California. But by 2021, in the middle of California’s most recent drought, it provided just 7%.
This year, billions of gallons of water are once again spinning turbines in power plants at huge dams like Shasta, Oroville and Folsom, and will be all summer and into the fall as the snowpack melts.
More hydropower means more clean electricity, less need to burn natural gas and other fossil fuels, less risk of blackouts during heat waves, and less smog and greenhouse gas emissions, experts say.
“It gives us more tools in the toolbox, more capacity to work with,” said Lindsay Buckley, a spokeswoman for the California Energy Commission, a state agency in Sacramento.
“It’s amazing. It was unexpected from Mother Nature. We’re going to make the best of it.”
After more than a dozen atmospheric river storms soaked Northern California between Christmas and March, hydropower production jumped 88% in California in the first three months of 2023, compared with the same time period last year, according to a report released in April by the U.S. Department of Energy. It is projected to increase 81% overall this year from 2022.
Over the past 20 years, California has been steadily increasing the amount of solar and wind power it requires utilities to purchase to reduce smog and greenhouse gas emissions. Those laws are working — about 35% of the state’s electricity is from renewable sources now like solar and wind, and 59% if large hydropower and nuclear are included.
But the greener power grid has come at a cost: Less reliability.
During severe heat waves, millions of Californians turn on their air conditioners, spiking demand for electricity. At night when the sun begins to set, solar farms go off line, even as demand remains sky high.
That’s what happened last September, when all-time heat records tumbled across California, including 118 degrees in Calistoga, and the day before 116 in Livermore and 109 in San Jose.
Blackouts were narrowly averted, but only after Gov. Gavin Newsom urged Californians to curb electricity use between 4 p.m. and 9 p.m., and relaxed air pollution rules to allow temporary natural gas-fired “peaker” plants and other generators to fire up.
Full reservoirs reduce the risk of a repeat this year, experts say.
“It gives us a clean resource we haven’t had as much of in the past few years to help meet the swings in electricity demands,” said Michael Wara, director of the Climate and Energy Policy Program at Stanford University’s Woods Institute for the Environment. “That means we can rely less on natural gas.”
To help improve reliability, state regulators have ordered utilities to put in place huge battery systems to store solar power on sunny days, then let it out on the grid at night. In 2019, California had 250 megawatts of battery storage. It has 5,000 megawatts now — roughly the same as 10 natural-gas fired power plants.
Newsom also signed a bill in September, over the objections of some activists, to keep Diablo Canyon, the state’s only nuclear power plant, open for another five years after its 2025 planned closure date.
To be sure, extra hydropower this year won’t solve all the state’s energy challenges.
The Pacific Northwest, which often sells hydroelectricity to California in wet years, didn’t have as rainy of a winter this year, and may want to buy some from PG&E, which owns 60 hydroelectric plants, and other dam owners.
California, which in most years imports about 25% of its power, shouldn’t say no, said Severin Borenstein, a professor of business at UC Berkeley.
“We definitely don’t want to set a standard where states refuse to sell to other states that are in desperate straits,” he said. “California is a big importer of electricity.”
In theory, all the hydropower this year should help PG&E ratepayers, because it is cheaper than other electricity sources. But details are not clear yet.
“We won’t know how much hydro has offset other costs to purchase power until early 2024 when all the data are in,” said PG&E spokesman Paul Moreno. “Factors like a hotter-than-normal, or cooler-than-normal summer could come into play.”
More hydropower also is likely to reduce air pollution.
Electricity generation makes up 16% of the state’s greenhouse gas emissions, the third-largest category behind transportation (38%) and industry (23%). Running water through turbines reduces emissions compared with burning natural gas.
It’s a similar story with smog. Although power plants are not a major statewide source of smog compared to vehicles and other sources, older plants can have major impacts on nearby neighborhoods.
Drought and heat waves in California worsen air pollution disproportionally in low-income areas, according to a new study published in March. Burning natural gas emits nitrogen oxides and particle pollution, or soot, which causes asthma, emphysema, heart problems and other health risks for residents living near power plants.
When hydropower drops, the study noted, that often means natural gas burning increases to keep the lights on.
“Drought is a driver of chronic pollution exposure,” said Jordan Kern, assistant professor of forestry and environmental resources at North Carolina State University and lead author of the study. “But heat waves are responsible for these incredible spikes in emissions in a short period of time.”
One of the more alarming symbols of California’s recent drought came at Lake Oroville, California’s second largest reservoir, where on Aug. 5, 2021, water levels fell so low that the power plant had to be shut down for the first time since it opened in 1967.
Then, the reservoir was 24% full. Today it is 94% full and the turbines are humming.
“The snowpack buys us time to put more batteries in the field,” said Wara. “Every year we can do that we get further away from the risk of blackouts during summer heat waves.”
