Washington State University researchers have documented an underappreciated suite of players in global warming: dams, the water reservoirs behind them, and surges of greenhouse gases as water levels go up and down.
Bridget Deemer, a doctoral student at Washington State University-Vancouver, 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. A fellow WSU-Vancouver student, Maria Glavin, sampled bubbles rising from the lake mud and measured a 36-fold increase in methane during a drawdown.
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 harbor biological activity that can produce large amounts of greenhouse gases. There are also some 80,000 dams in the United States alone, according to the U.S. Army Corps of Engineers National Inventory of Dams.
“Reservoirs have typically been looked at as a green energy source,” says Deemer. “But their role in greenhouse gas emissions has been overlooked.”