Small dams may contribute much more to greenhouse gas emissions than was previously thought, according to new research — the sediments that build up behind dams release more methane than was previously known.
The findings add to the growing body of evidence suggesting that dams — particularly large hydroelectric dams — contribute significantly to global greenhouse gas emissions.
The press release explains:
Andreas Maeck and colleagues point out that the large reservoirs of water behind the world’s 50,000 large dams are a known source of methane. Like carbon dioxide, methane is one of the greenhouse gases, which trap heat near Earth’s surface and contribute to global warming. Methane, however, has a warming effect 25 times more powerful than carbon dioxide. The methane comes from organic matter in the sediments that accumulate behind dams. That knowledge led to questions about hydroelectric power’s image as a green and nonpolluting energy source. Maeck’s team decided to take a look at methane releases from the water impoundments behind smaller dams that store water less than 50 feet deep.
The research was done by measuring and analyzing total methane release from the water impounded behind six small dams on a European river. “Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7 percent,” the report states. The report also notes that “such emissions are likely to increase due to a boom in dam construction fostered by the quest for new energy sources and water shortages.”
The researchers received funding from the German Research Foundation.
The new findings were published in the ACS journal Environmental Science & Technology.