Hydroelectric Power Isn’t as Green as We Thought

Building a dam to generate electricity from water sounds like a renewable energy no-brainer. But the resulting reservoirs may have a more detrimental effect on our climate than we realized.

According to research from Washington State University that’s due to be published in the journal BioScience next week, the reservoirs formed by dams emit more methane per unit area than expected. As Science reports, the measurement of its release from these kinds of bodies of water has been more difficult than for other gases, like carbon dioxide, because instead of diffusing out of the water it emerges in bubbles.

New techniques to measure methane bubbles, though, have allowed the Washington State University team to calculate the rate of release more accurately. And the results show that reservoirs typically emit 25 percent more methane than previously thought. That may not sound too bad, but it’s worth remembering that methane is around 30 times more potent as a greenhouse gas than carbon dioxide, so even small quantities can have a great impact.

Meanwhile, the world is building new hydroelectric installations apace. According to a paper published in the journal Aquatic Sciences last year, as many as 3,700 hydropower dams will come online in the next 10 to 20 years. That is expected to provide over 700 gigawatts of extra capacity around the world—about 70 percent of the the total installed capacity across the whole of the U.S.

Clearly, hydroelectric plants are by no means as polluting as fossil-fuel energy production. But their rapid construction over the coming years will have a larger impact on our emissions than we hoped. Dam it.

(Read more: Science, Aquatic Sciences, “What Do You Do When a Gold Mine Runs Out? Turn It into a Power Plant”)