Destructive hurricanes and devastating wildfires aren’t the only effects of climate change. Rainfall patterns are also being altered, and many parts of the country are experiencing severe drought. That is having an adverse effect on electricity, as hydropower has less water to generate energy.

According to a recent report from the U.S. Energy Information Administration (EIA), nearly three-quarters of the country is experiencing drought or conditions that approach drought, which is also curtailing the output of hydropower.

The EIA’s most recent Short-Term Energy Outlook (STEO) was published on Nov. 13. It forecasts electricity generation from U.S. hydropower plants in 2024 to be 13% less than the 10-year average. That would represent the least amount of electricity generated from hydropower in more than 20 years, going all the way back to 2001.

The STEO notes that “extreme” and “exceptional” drought conditions have been affecting different parts of the United States. As of the end of September, 72.6% of the continental United States was experiencing dryer-than-normal to exceptional drought conditions.

The reports notes that the Pacific Northwest has been especially hard hit. It cites figures from the U.S. Department of Agriculture’s Basin Outlook Reports, which show that reservoir storage at the end of September was extremely low in these states. Specifically, they were down to 48% of capacity in Oregon, 67% in Washington, 76% in Montana and 60% in Idaho.

Because these states are home to most U.S. hydropower capacity, the severe lack of rainfall and diminishing reservoir storage are impacting power generation there. The STEO expects hydropower generation in the Northwest electricity region, which includes states in the Columbia River Basin and parts of other Rocky Mountain states, to total 101.8 billion kilowatt-hours (kWh) in 2024. That is a 23% decrease from the 10-year average of 132.8 billion kWh and a 1% decrease from 2023.