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Reservoirs play substantial role in global warming

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Staff Writer | October 10, 2016
Washington State University researchers say the world's reservoirs are an underappreciated source of greenhouse gases.
Small lake
Ecology   More greenhouse gas production than Canada
They are producing the equivalent of roughly 1 gigaton of carbon dioxide a year, or 1.3 percent of all greenhouse gases produced by humans. That's more greenhouse gas production than all of Canada.

Writing in next week's journal BioScience, the WSU researchers say reservoirs are a particularly important source of methane, a greenhouse gas that is 34 times more potent than carbon dioxide over the course of a century.

Reservoir methane production is comparable to rice paddies or biomass burning, both of which are included in emission estimates of the Intergovernmental Panel on Climate Change, the leading international authority on the subject.

John Harrison, co-author and associate professor in the WSU Vancouver School of the Environment, last month attended a meeting in Minsk, Belarus, to discuss including reservoir emissions in a planned 2019 IPCC update of how countries report their greenhouse gas inventories.

"We had a sense that methane might be pretty important but we were surprised that it was as important as it was," said Bridget Deemer, WSU research associate and lead author. "It's contributing right around 80 percent of the total global warming impact of all those gases from reservoirs. It's a pretty important piece of the budget."

The BioScience analysis, which drew on scores of other studies, is the largest and most comprehensive look to date at the link between reservoirs and greenhouse gases, Harrison said.

"Not only does it incorporate the largest number of studies," he said. "It also looks at more types of greenhouse gases than past studies."

Acre per acre, reservoirs emit 25 percent more methane than previously thought, he said.

The researchers acknowledge that reservoirs provide important services like electrical power, flood control, navigation and water.

But reservoirs have also altered the dynamics of river ecosystems, impacting fish and other life forms. Only lately have researchers started to look at reservoirs' impact on greenhouse gases.