Droughts are cutting into California’s hydropower. Here’s what that means for clean energy.

Droughts are cutting into California’s hydropower. Here’s what that means for clean energy.

The droughts that swept across the western US in 2021 sparked wildfires and damaged crops. The historic shortage of water had an impact on California’s main source of renewable energy, hydropower.

Electricity generation from California hydropower plants was down 48% from the 10-year average, according to new data from the Energy Information Agency. And 2022 is looking even worse.

Hydropower is the world’s leading source of renewable energy, making up about 17% of electricity generation in 2020, but droughts in various regions are making it harder to rely on. It is a low-carbon source for power and helps to limit carbon dioxide emissions. This is especially important because fossil fuels are often used to compensate for the loss of a hydropower plant.

Hydropower plants made up about 19% of electricity generation in California in 2019. Most of them are located in the state’s northern region, where snowpack melts from the mountains to feed the reservoirs. The reservoirs have been drying up due to droughts in the past two years. The second-largest one in the state, Lake Oroville, saw water levels drop so low in 2021 that the hydropower plant there was shut down for the first time in its history.

The lost power can’t easily be replaced with renewable sources that fluctuate during the day, like wind and solar. When California’s hydropower capacity dropped from 2019 to 2020, much of the difference was replaced by natural-gas generation and electricity imports from other states, according to data from the California Energy Commission.

Hydropower is often criticized for its environmental impact. Dams can disrupt ecosystems. California doesn’t currently include large hydropower plants in its renewable-power targets. But regardless of how it’s categorized, hydropower is a lower-emissions alternative to fossil fuels.

During high-stress periods on the grid, the decreased reliability of hydropower can cause problems, according to Brian Tarroja ,, an energy researcher at University of California, Irvine.

Last Year, the Bootleg fire in Oregon caused severe damage to transmission lines in California. This was at a time of increased electricity demand and high temperatures. Running hydropower plants at their drought-reduced capacity while ramping up natural-gas plants was barely enough to keep the power on.

These difficulties are likely to persist, Tarroja states. Climate change is changing rainfall patterns and causing higher temperatures even though overall precipitation remains constant. The effects are likely to challenge hydropower in the coming decades. Places with high hydropower levels may need to begin planning for the impacts of climate change on power generation. That’s not just California: droughts in Brazil and China have also threatened hydropower capacity in recent years.

There will be some natural variation from year to year, but reprieve isn’t likely to come soon. In an email, Aleecia Gutierrez, deputy head of the California Energy Commission’s Energy Assessments Division, stated that reservoir levels are “considerably worse” than last year.

Other renewable energy sources could eventually provide more reliable power to the grid, bolstered by technologies like grid-scale battery installations. For now, however, hydropower losses will likely lead to more electricity generation from fossil fuels and more emissions.

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