In July,UN Secretary Ban Ki-Moon highlighted the role of hydropower in boosting the use of renewable energy globally, when he visited a nonprofit institute in China that helps emerging nations develop and build hydropower plants. Many countries consider hydroelectricity a clean source of power because it doesn’t involve burning dirty fossil fuels. But that’s far from true. Hydropower is a significant source of greenhouse gas emissions: a new study shows that the world’s hydroelectric dams are responsible for as much methane emissions as Canada.
The 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. What’s more, none of these emissions are currently included in global greenhouse gas inventories. These are already revealing a worrisome future in which rising global temperatures will likely cause environmental changes such as rising sea levels and stronger hurricanes, which could uproot communities and intensify competition for food and other resources.
“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.