Tropical Hydro May Be Large Greenhouse Gas Generator

Yesterday on EcoTalk, the national radio show hosted by Betsy Rosenberg, one of the guests, Patrick McCully, Executive Director of International Rivers Network, said that scientific studies have shown that building hydropower dams in tropical areas results in huge emissions of greenhouse gases, particularly methane, but also carbon dioxide. This of course is in direct contrast to the way we usually think about hydro which is as a clean energy source that is an alternative to burning fossil fuels to generate electricity. In the United States at least, most of criticism of hydro has revolved around environmental issues such as the loss of wild rivers and the filling up of spectacular canyons with water. According to McCully, the building of hydropower dams in the tropics creates a much different problem than building such dams here in a temperate climate. He said that in the tropics, various factors in the reservoirs created behind the dams such as high water temperatures and low oxygen levels at the bottom of the reservoirs result in large amounts of greenhouse gases being created and eventually released from bubbles when the water flows through the spillways. Also, in the tropics when the impounded water behind the dam floods the surrounding areas the thick vegetation dies and greenhouse gases are generated in the decomposition process. This appears to be an issue that deserves more attention as efforts are undertaken to find sources of energy that do not contribute to global warming.