Whoops—Dams and Reservoirs Release Tons of Greenhouse Gases

New study shows reservoirs are actually a major source of carbon emissions

A reservoir on the Snake River in Washington state Shelly Hanks, WSU Photo Services

For years, clean energy advocates have pointed towards hydroelectricity as an important alternative to gas, coal and nuclear power plants. But a new study suggests that the dams and reservoirs commonly associated with this clean energy source are actually pumping a significant amount of carbon emission into the air, Maddie Stone reports for Gizmodo.

Curbing carbon emissions and other greenhouse gases has been a major goal for countries around the world as governments work together to limit the rising global temperatures. As emissions continue to rise, scientists have searched for the sources of these gasses, but significant gaps still remain in tracking their origins.

The new study could fill in some of these gaps. Researchers analyzed more than 200 past studies and found that the reservoirs attached to hydroelectric dams around the world could actually be among the biggest contributors to greenhouse gases due to pockets of methane bubbling beneath the surface.

“We synthesized all known estimates from reservoirs globally, for hydropower and other functions, like flood control and irrigation,” Bridget Deemer, a researcher at Washington State University (WSU) tells Chris Mooney for the Washington Post. “And we found that the estimates of methane emissions per area of reservoir are about 25 percent higher than previously thought, which we think is significant given the global boom in dam construction, which is currently underway.”

Scientists have long known that methane is a major problem when it comes to global warming, but this is the first time man-made reservoirs have been identified as a significant source. When reservoirs are created for storing water or producing hydroelectric energy, they also create the perfect environment for carbon dioxide- and methane-producing microbes to snack on decomposing natural materials at the bottom of these artificial lakes. At the same time, the rivers that feed these reservoirs also bring in plenty of new microbe chow. These gases then bubble up to the reservoir’s surface and enter the atmosphere, Mary Beth Griggs reports for Popular Science.

According to Deemer’s study, which will be published next week in the journal BioScience, reservoirs around the world are responsible for releasing about a gigaton of carbon dioxide into the atmosphere every year. That’s 1.3 percent of all greenhouse gases that humans produce annually and more than all of Canada’s cars, factories and power plants emit every year, according a university press release.

“We’re trying to provide policymakers and the public with a more complete picture of the consequences of damming a river,” John Harrison, another study author and WSU researcher, tells Mooney.

As world leaders continue to negotiate towards a new climate agreement, it’s important to take this unexpected greenhouse gas source into consideration.

Get the latest stories in your inbox every weekday.