SOURCE: National Geographic

DATE: December 21, 2018

SNIP: During the darkest days of the drought that has gripped the western U.S. since the early 2000s, fires raged and crops withered. Dust storms rolled across plains and valleys. And rivers shriveled from north to south.

But the drought had less obvious effects on climate and the environment, too: Low river flows drastically hampered the amount of carbon-free electricity [sic] that could be produced by the thousands of hydroelectric power plants dotted along rivers and reservoirs across the West.

If energy utilities can’t get the power they need from hydroelectric sources, they have to fill that gap with something else. Most of the time, the researchers found, the utilities fell back on carbon-emitting sources like natural gas and coal to fill their power needs.

Now, a group of researchers has done the carbon math to see how big that effect was. They figured out that an extra 100 megatons of carbon ended up in the atmosphere because utilities had to use carbon-emitting power sources instead of hydroelectric power during drought, added up over the 15 years they studied. That’s the equivalent of adding about 1.4 million cars to the road for every one of those years.

“Droughts are going to get worse, and that could mean more natural gas and coal being burned,” says Peter Gleick, a water expert at the Pacific Institute, a research organization in Oakland.

Related: Hydroelectric dams emit a billion tonnes of greenhouse gases a year, study finds