Dams Contribute to Climate Change

[IDemo]

Washington State Univ. 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 Univ.-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 U.S. 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.”

http://www.laboratoryequipment.com/news/2012/08/dams-contribute-climate-change

[FBaggins]

1. What about the carbon sink on the other end?

Dams are not just drawn down to provide power generation. Most large dams (or rather the large reservoirs that they create) serve an at-least-as-important purpose of water storage for the dry season. The down-stream area is much greener (including non-crop plant life) than it would be without the dam up-stream.

You can't look at one side of the equation and ignore the other.

Also... "methane emissions jumped 20-fold" doesn't mean as much without the amounts involved. 20-fold could still be far FAR smaller than the reduced climate impact of generating power this way vs. the common alternatives.

[eppur_se_muova]

2. Not entirely overlooked ...

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=364x2741672

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x101846

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x95870

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=115x212128