Hydropower out of whack thanks to record heat and precipitation

In California, hydropower output is expected to double this year. But in the hydro-dependent Northwest, abnormal heat could cause it to shrink by 19%.
By Julian Spector

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dam and reservoir
A view down the spillway of the Shasta Dam into the Sacramento River in Shasta Lake, California (Michael Macor/The San Francisco Chronicle via Getty Images)

Hydropower, unlike wind and solar, can deliver power around the clock, on demand. But this renewable energy source’s reputation for reliability is running up against dramatic regional fluctuations from extreme weather.

The U.S. Energy Information Administration just lowered its 2023 nationwide hydropower forecast by 6% from last year’s production level. An extremely hot summer quickly sapped snowmelt in several regions, pushing down their reserves for hydro generation through the end of the year. But electricity production operates on a local or regional basis, and that single-digit national change masks significant variation within specific regions.

The Northwest is experiencing the most foreboding swing: Hydropower production for the first half of the year fell 24% from the same period in 2022. The EIA predicts a 19% decrease for the whole year compared to last year. That’s for a region that produces roughly half of all U.S. hydro generation — the EIA defines the Northwest, for this purpose, as running inland from the Pacific through Montana and down to Colorado.

Meanwhile, California’s hydro production is expected to double compared to 2022 after historic snowfall in the Sierra Nevada mountains last winter. That’s good news for grid operators in California: The newly abundant hydro reserves nicely balance the state’s massive solar fleet by producing power day and night. The rest of the country, though, is heading for a third year of incremental hydropower decline.

Rainfall has always varied from year to year, and hydropower production waxes and wanes with it. That didn’t matter so much when utilities could simply burn coal or gas to make up the difference. But now utilities are switching from fossil-fueled plants to as much clean generation as possible to meet corporate climate goals (and assist U.S. national climate commitments). The U.S. needs every bit of clean energy it can muster, at the same time that heat waves have gotten measurably more intense. Radical dips in hydropower production make it harder to rely on that resource to balance out the weather-dependent swings of wind and solar.

The stakes are highest in the Northwest, where Idaho, Oregon and Washington all made a majority of their electricity from hydropower last year. Idaho Power, for instance, views its hydro fleet as crucial to achieving a corporate goal of 100% clean electricity, as recently explored in a Los Angeles Times article. Hydro-centric utilities need to ensure they have sufficient power supply from other sources when their hydro production drops 20% in a given year, but preferably without spending too much money on power plants that aren’t needed the rest of the time. Idaho Power is getting its first large-scale grid batteries this year, but it will be a while before that technology matches the scale and cost-effectiveness of hydro for on-demand, fossil-free power.

Outside the U.S., other countries are grappling with even more extreme losses in hydropower production this year. China, which generates roughly one-third of the world’s hydroelectricity, will produce 7% less than the year before due to droughts, according to a forecast from Economist Intelligence. Hydro production will fall by 8% in Vietnam, which typically gets 30% of its electricity from dams.

This summer was quantifiably more extreme than others — NASA recorded it as the hottest summer since the records began in 1880, the result of an El Niño phenomenon exacerbating long-term warming from climate change. If more summers follow that pattern, hydro headaches will become a regular part of running the grid — and something that grid operators could seek to address with emerging, cheaper alternatives for on-demand clean energy.

Julian Spector is a senior reporter at Canary Media. He reports on batteries, long-duration energy storage, low-carbon hydrogen and clean energy breakthroughs around the world.