The Energy Information Administration forecasts the U.S. this year will generate the least amount of hydroelectricity in nearly a quarter of a century because of widespread drought.

Hydropower production has dropped to its lowest level since 2001 and is expected to end the year 13% below the 10-year average.

Hydropower has been especially curtailed in the Northwest region, where output will be down 23% from the 10-year average. The region takes in Rocky Mountain states, as well as Oregon, Washington and northern California.

Fossil fuel-fired power plants have picked up the slack to meet peak demands and back up intermittent wind and solar power, Northwest Public Power Association executive director Kurt Miller said.

“Almost inevitably, you’re really looking at natural gas,” Miller said. Without the natural gas-fired plants, “we’d be hosed.” 

Hydropower will supply 101.6 billion kilowatt-hours in the Northwest and Rocky Mountains, or 28% of the total electricity, according to EIA’s short-term energy outlook.

The agency expects the region’s hydropower production will rebound to 124 billion kilowatt-hours next year, a 22% increase. Natural gas-fired electricity will decline by 15%, EIA predicts.

The National Weather Service’s Climate Prediction Center predicts a La Nina will form this winter. La Nina years are generally wet in the Northwest. An El Nino, which has the opposite effect, prevailed last winter.

Some 44% of 11 Western states was in a drought Thursday, according to the U.S. Drought Monitor.

“We’ve known since early last winter this was not going to be a good hydropower year,” Miller said.

Droughts definitely affect demand for natural gas, Northwest Natural Gas CEO Dan Kirschner said.

“If the water is not there, you have to have something else,” he said. “I think you could be hearing in the next year or two we need more gas-fired generation in the region.”

Washington generated more hydropower than any other state in 2023, according to EIA. Washington’s reliance on renewable hydropower could ironically complicate aspirations to make the state’s electric grid carbon-free by 2045.

A study last year in the Proceedings of the National Academy of Sciences documented that fossil fuel power plants in the West ramp up in droughts.

Fossil fuel plants increased production by up to 65% in drought months, according to the study led by Minghao Qiu of Stanford University.

Electric grids heavily dependent on hydropower will become harder to decarbonize if droughts become more frequent, even if other renewable forms of energy are aggressively developed, the study found.

Batteries are currently limited to supplying energy for about four hours when wind and solar production are low, Miller said. “They’re not long-lasting enough to fill in the gaps,” he said.

A Florida company, Rye Development, has proposed a pump-storage power plant in south-central Washington to supply on-demand, carbon-free electricity. The Yakama Nation, historic preservationists and environmental groups oppose the project because of its potential impact on tribal cultural sites.