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Sediment Behind Dams Creates Methane 'Hot Spots'

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A study shows damming a river creates hydroelectric power, provides a reservoir for drinking water and recreation -- and contributes to global warming more than previously thought.

The world's 50,000 large dams are a known source of methane, which bubbles up from the organic matter in the sediment accumulating behind the barrier. Methane is a greenhouse gas, with a warming effect 25 times more powerful than carbon dioxide.

Andreas Maeck, a graduate student at the University of Koblenz in Germany, led team looking at methane releases from small dams that store water less than 15 meters deep. There are millions of these dams around the world, and the team found that the accumulation of sediment correlated with methane production in the water. The researchers report that these methane 'hot spots' have the potential to increase emissions of the gas by up to 7 percent, a much higher amount than previously believed.

Writing in the journal Environmental Science & Technology, the team warns such emissions are likely to increase due to a boom in dam construction fostered by the quest for new energy sources and water shortages.

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