A new study by researchers from Washington State University and the University of Quebec at Montreal looked at greenhouse gas emissions from water reservoirs. It is perhaps surprising to think that water reservoirs are a source of greenhouse gas emissions at all, but that much was already known. The new study found that those emissions are actually around 29% higher than previously thought.
Overall, the researchers found that the world’s water reservoirs annually produce methane, carbon dioxide, and other greenhouse gases at an amount equivalent to 1.07 billion tons of carbon dioxide. That is a small fraction of the 36 billion tons produced by fossil fuels and other industrial sources, but it is by no means a negligible amount. In fact, it is more greenhouse gases than emitted by the entire country of Germany, which is the world’s sixth largest emitter.
Decomposing plant matter near the bottom of reservoirs fuels the production of methane, which is far more potent than carbon dioxide in warming the atmosphere. This methane degassing accounts for about 40% of emissions from reservoirs.
The study is particularly important because it may be possible to reduce methane emissions from reservoirs by selectively only withdrawing water from near the reservoirs’ surface, which tends to be relatively methane-poor compared to greater depths. In a related study, reducing withdrawal depth by 10 feet in a Malaysian reservoir reduced methane degassing emissions by 92%.
Human-generated greenhouse gas emissions come from a surprisingly wide range of sources and it is worthwhile studying as many of them as possible in the hope of finding additional ways to reduce the total.
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Greenhouse gas emissions from water reservoirs higher than previously expected
Photo, posted July 22, 2016, courtesy of Iain Merchant via Flickr.
Earth Wise is a production of WAMC Northeast Public Radio.