Hydroelectric dams have had a devastating impact on anadromous fish populations, from inundating spawning areas to changing historic river flow patterns and raising water temperatures, and most importantly blocking passage of salmon and steelhead between the streams and Pacific Ocean.
But dam apologists often point to the carbon emission avoidance of using hydroelectric power. A new study from Washington State University finds that methane, which is at least 34 times more potent than another greenhouse gas, carbon dioxide, makes up 80% of the emissions from water storage reservoirs created by dams.
“I think this study shows that dams as a source of energy aren’t without their greenhouse gas costs,” says Bridget Deemer, a research ecologist at the US Geologic Survey, who led the study during her prior position as a research associate at Washington State. “Even though it’s a renewable source of energy, people should keep the greenhouse gas side of the picture in mind when making planning and policy decisions regarding dams.”
The research, which examines 100 recent studies on greenhouse gas emissions from 267 large reservoirs around the world, also calls into question the wisdom of building more hydroelectric dams as countries try to nix their dependence on coal, natural gas and oil. An estimated 3,700 new dams are proposed or under construction around the globe, the study reports. It suggests the hydropower industry will need to control its emissions.
According to the Seattle Weekly, some reservoirs emit more greenhouse gases than fossil-fuel-based energy providers, such as natural-gas power plants.