Heat and drought are sucking US hydropower dry

The amount of hydropower generated in the Western US last year was the lowest it’s been in more than two decades. Hydropower generation in the region fell by 11 percent during the 2022–2023 water year compared to the year prior, according to preliminary data from the Energy Information Administration’s Electricity Data Browser — its lowest point since 2001.

That includes states west of the Dakotas and Texas, where 60 percent of the nation’s hydropower was generated. These also happen to be the states — including California, Nevada, Arizona, and New Mexico — that climate change is increasingly sucking dry. And in a reversal of fortunes, typically wetter states in the Northeast — normally powerhouses for hydropower generation — were the hardest hit. You can blame extreme heat and drought for the drop in hydropower last year.

This creates a vicious cycle: drought reduces the amount of clean energy available from hydroelectric dams. To avoid energy shortfalls, utilities wind up relying on fossil fuels to make up the difference. That leads to more of the greenhouse gas emissions causing climate change, which makes droughts worse.

Heat was another problem in the Western US during the last water year, which starts over in October in order to account for both winter snow and summer rain. Temperatures rose a startling 30 degrees Fahrenheit above normal in the Pacific Northwest during a May 2023 heatwave.

Western states typically rely on slowly melting snowpack for water during dry summer months, but much of that snowpack vanished with the heat in May. That left the Northwest with below-average water supply for the rest of the water year. Hydropower in Washington and Oregon fell by at least 20 percent during the last water year. Combined, the two states normally make up 37 percent of the nation’s hydropower capacity.

California, in contrast, experienced a bit of a reprieve from a megadrought that has plagued the Southwest for some two decades. A series of atmospheric river storms in 2023 were a double-edged sword, dropping record amounts of snow and rain in parts of the state while also causing disastrous flooding in communities more accustomed to dry weather. But while hydropower production rose in the Golden State last year, it’s forecast to fall again this year.

Image: US Energy Information Administration

The Energy Information Administration expects 12 percent less hydropower production across the Western US in 2024 compared to the previous year. And whenever there’s less hydropower, there’s usually more pollution from gas and coal-fired power plants that ramp up generation to fill in the gaps.

We saw that happen on a global scale in 2023. Energy-related greenhouse gas emissions across the world increased by 410 million metric tons last year, roughly equivalent to adding the pollution from more than 1,000 new gas-fired power plants. Why? Drought created an “exceptional shortfall” in hydropower — especially in the US and China, the countries that produce the most planet-heating pollution. That alone was responsible for 40 percent of the rise in global emissions last year, according to the International Energy Agency.