Global Challenges/Chemistry Solutions

Confronting Climate Change: Sediment trapped behind dams makes them ‘hot spots’ for greenhouse gas emissions

January 13, 2014

dam
Millions of small river dams around the world are contributing to the rise in the greenhouse gases linked to global climate change.
Credit: iStockphoto/Thinkstock

Summary

With the “green” reputation of large hydroelectric dams already in question, scientists are reporting that millions of smaller dams on rivers around the world make an important contribution to the greenhouse gases linked to global climate change. Their study, showing that more methane than previously believed bubbles out of the water behind small dams, appears in ACS’ journal Environmental Science & Technology.

Today’s challenge was discovered by scientists interested in the greenhouse gas emissions of small dams. Their study shows that more methane than previously thought bubbles out of the water trapped behind these structures, which number in the millions around the globe.  The report appears in the ACS journal Environmental Science & Technology.

The researchers point out that the 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.

Andreas Maeck, Ph.D., who’s with the University of Koblenz-Landau in Germany, and his team decided to take a look at methane releases from the water impoundments behind smaller dams that store water less than 50 feet deep 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. Such emissions are likely to increase due to a boom in dam construction, which has been fostered by water shortages and the quest for new energy sources.”

Smart Chemists/Innovative Thinking

Smart chemists. Innovative thinking. That’s the key to solving global challenges of the 21st century. Please check out more of our full-length podcasts on wide-ranging issues facing chemistry and science, such as promoting public health, developing new fuels and confronting climate change, at www.acs.org/GlobalChallenges. Today’s podcast was written and narrated by Christine Suh at the American Chemical Society in Washington.

Andreas Maeck, Ph.D.
Andreas Maeck, Ph.D., University of Koblenz-Landau, Germany