WSU scientists say manmade reservoirs are a contributor to global warming

NewImageIsn’t everything we do a contributor to “manmade global warming”? Ranchers cannot even raise beef without being accused of cow farts causing global warming. Sheesh! 

Reservoirs behind dams release significant amounts of greenhouse gases, and their output should be counted in future emissions reporting, says a new study from Washington State University.

More than 1 million reservoirs worldwide produce about 1.3 percent of the greenhouse gas emissions generated by human-caused activity, according to the study. The volume is roughly equivalent to 1 gigaton of carbon dioxide annually, which is more than Canada’s yearly production.

“While reservoirs are often thought of as ‘green’ or carbon-neutral sources of energy, a growing body of work has documented their role as greenhouse gas sources,” researchers wrote in the study that will be published next week in the journal BioScience.

The WSU study noted that reservoirs flood large areas, submerging organic material that produces greenhouse gases as it decomposes. Methane, for instance, is produced when microorganisms breakdown organic matter in parts of the reservoir where oxygen isn’t present.

Reservoirs are generally warmer than free-flowing rivers and they collect nutrients that wash downstream. Reservoirs with high levels of algae and plant growth also had the highest levels of greenhouse gas emissions, the WSU study said.

Reservoirs produce about 25 percent more methane per acre than previously thought, said Bridget Deemer, a research associate at WSU-Vancouver and the study’s lead author. That’s significant, because methane is a powerful greenhouse gas, 34 times more potent than carbon dioxide over the course of a century.