Dams, reservoirs are new global warming culprits

Washington: American researchers have found that fluctuating water levels in dams and reservoirs emit large amount of greenhouse gases, the main culprits of global warming. 

    Researchers at Washington State University-Vancouver have documented the emission of greenhouse gases like methane, as water levels go up and down in dams and reservoirs. 
    Methane is 25 times more effective than carbon dioxide at trapping heat in the atmosphere. And while dams and the water behind them cover only a small portion of the earth's surface, they harbour biological activity that can produce large amounts of greenhouse gases. 
    "Reservoirs have typically been looked at as a green energy source. But their role in greenhouse gas emissions has been overlooked," researcher at Washington State University Bridget Deemer said. 
    Researchers measured dissolved gases in the water column of Lacamas lake in Clark County and found methane emissions jumped 20-fold when the water level was drawn down. They also sampled bubbles rising from the lake mud and measured a 36-fold increase in methane during a drawdown. 
    There are nearly 80,000 dams in the United States alone, according to the US Army Corps of Engineers National Inventory of Dams. 
    A previous study estimated that the ability of terrestrial ecosystems to act as carbon sinks, storing greenhouse gases, could be one-fourth less than estimated once emissions from reservoirs are considered. 
    This is the first study to demonstrate and quantify the relationship between water-level drawdowns and greenhouse gas releases. PTI

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