The study claims that man-made lakes and reservoirs are actually have a very big effect on our planet.
A remarkable new study out of the University of Washington is claiming that there are huge methane emissions from man-made lakes and reservoirs, and they may be contributing greatly to global warming. The study, which involved an analysis of about 200 studies and was published in the journal BioScience, says that man-made hydropower reservoirs near dams, far from being a clean energy source, are actually contributing to greenhouse gas emissions and are resulting in a net increase in carbon dioxide.
The study included a multinational team of researchers who found that these reservoirs are pumping out a billion tons of carbon dioxide each year, which makes up 1.3 percent of the total emitted world wide and is larger than entire amount emitted annually by Canada.
This happens because when valleys are flooded to make these reservoirs, microbes eat the organic matter in the soil and produce methane.
“If oxygen is around, then methane gets converted back to CO2,” Washington State researcher John Harrison said according to a Post report. “If oxygen isn’t present, it can get emitted back to the atmosphere as methane.”
They found that methane made up 79 percent of all carbon dioxide equivalent emissions from reservoirs, whereas about 17 percent came from CO2 and 4 percent from nitrous oxide.
“There’s been kind of an explosion in research into efforts to estimate emissions from reservoirs,” researcher Bridget Deemer of Washington State University, first author on the study, added to the Post. “So we synthesized all known estimates from reservoirs globally, for hydropower and other functions, like flood control and irrigation.”
In addition, methane emissions may be 25 percent higher than had been thought.
The study is a good example of just how much of an effect man-made things like reservoirs can have on the environment. Even seemingly benign acts like creating a reservoir can have tremendous effects that we don’t recognize.
“There’s been a growing sense in the literature that methane bubbles are a really important component of the total emissions from lake and reservoir ecosystems,” Deemer said in the statement. “This study revisited the literature to try and synthesize what we know about the magnitude and control on methane emissions and other greenhouse gases—carbon dioxide and nitrous oxide.”
The organic matter is in the form of nutrients like nitrogen and phosphorous, and a lot can come from upstream rivers, further increasing greenhouse gas production. BioScience published a paper in 2000 that asserted reservoir greenhouse gases may contribute quite a bit to global warming, and since then there has been a big increase in papers looking at this issue.
The WSU statement says that their researchers were the first to consider methane bubbling in these greenhouse gas emission models. While young, tropical reservoirs tend to emit more methane, when it comes to the total effect on global warming, how biologically productive it is is usually a bigger sign.
“The authors also report higher per-area rates of methane emission from reservoirs than have been reported previously,” the statement adds. “This means that acre-for-acre the net effect of new reservoirs on atmospheric greenhouse gases will be greater than previously thought. Reservoir construction around the globe is expected to proceed rapidly in coming decades.”