The list of global warming suspects has got longer with researchers documenting the role dams played in global warming and the surging levels of greenhouse gases as water levels go up and down.
Bridget Deemer, doctoral student at Washington State University (WSU)-Vancouver, US, measured dissolved gases in the water column of Lacamas Lake in Clark County and found methane emissions surged 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 per cent rise in methane levels during a drawdown, a university statement said.
Methane is around 25 times more effective than carbon dioxide at trapping heat in the atmosphere. Also while dams and the water behind them covered only a small portion of the earth's surface, they harboured biological activity that could give out large amounts of greenhouse gases.
According to US Army Corps of Engineers' National Inventory of Dams, there were around 80,000 dams in the US alone. Demeer said while reservoirs had typically been looked at as a green energy source, their role in greenhouse gas emissions had been overlooked.
Deemer and Glavin's findings would be on display this week at a poster session at the national meeting of the Ecological Society of America in Portland.