Dams have always been seen as a green alternative that allows us to reduce our dependency on fossil fuels. While its true that dams are a renewable source of energy, that doesn’t mean that they do not have an impact on climate change. And as it of turns out to be cause, their impact has been underestimated by earlier assessments. New studies have revealed that they generate more methane emissions than previously thought.
“We estimate that dams emit around 25% more methane by unit of surface than previously estimated,” said Bridget Deemer, from the School of Environment at the Washington State University in Vancouver, and lead author of the study.
Let’s keep in mind that methane is a very powerful greenhouse gas that affects the climate very quickly. Our increasing methane production is a major contributor to the climate change that we’re currently experiencing.
”The most recent assessment of the Intergovernmental Panel on Climate Change states that methane has a warming impact 72 times higher than carbon dioxide if measured over 20 years, and 25 times higher measured over 100 years. Using these IPCC “global warming potential” (GWP) estimates means that one year’s methane emissions from large dams, as estimated by Lima, have a global warming impact over 100 years equal to that of 2.6 billion tonnes of carbon dioxide. (Under the Kyoto Protocol, countries estimate their total warming impact using the 100 year GWPs). Over 20 years, the warming impact of annual large dam methane emissions is equivalent to 7.5 billion tonnes of carbon dioxide” – Source : internationalrivers.org
But how can a dam produce greenhouse gases if there are no farting cows or burning of organic matter involved? Organic material like trees and grass is carried by the river and deposited on the bottom of the reservoir where bacteria decompose it and in the process release methane. The powerful greenhouse gas is carried to the surface as bubbles and is released into the atmosphere.
A lot of these bubble-based emission haven’t been taken into consideration in previous studies and assessments. The study takes into the analysis provided by more than 250 dams and concludes that dams emit more methane than natural lakes and wetlands.
According to the study, the altitude of the dam can play a big role on the amount of methane that it produces. Algae that proliferates in downstream dams may receive more nutrients such as nitrogen or phosphate, and therefore produce more methane. The research provides valuable information about the future building of more efficient dams, that generate less greenhouse gases. But building more dams in the upstream is not necessarily a great solution either. When the dams are positioned higher on the stream of a river they end up impacting a bigger portion of it. It’s also important to note that dams that are built in the tropical latitudes can have much greater emissions. ”Large hydro-power reservoirs in the tropics can have a higher global warming impact per kilowatt-hour generated than fossil fuels, including coal. Philip Fearnside, of Brazilian government research institute INPA, estimates that in 1990 the warming impact of hydro-power dams in the Amazon was equal to that of between 3 and 54 natural gas plants generating the same amount of energy.”Source : internationalrivers.org
Europe has 23,000 dams, of which more than 2,000 are large, active hydroelectric structures. In the Balkans, close to 2,700 new dams are planned – mainly small and medium-sized. Environmental organizations challenge the notion that smaller dams are friendlier than large ones. “The environmental consequences are the same, regardless of size, and small dams do not produce much electricity at all”, says Cornelia Wieser of the Austrian organization Riverwatch. “The 21,000 small dams make up 91% of the total, but they generate only 13% of all hydro-power.” – Source : technologist.eu
The greenhouse gas emission generated by dams are just one of many negative impacts that obstructing the flow rivers is having on the environment. I don’t want to say that the technology shouldn’t have a place in the future of our energy production, but should be aware of its various negative effects and maybe reconsider its green label. The Blue Heart of Europe is a massive information campaign launched by the company Patagonia that puts the focus on the future of last pristine rivers in Europe, home to unique and vital ecosystems.They have produced a documentary movie that raises awareness about the various environmental impacts of dams and it also calls for action. Find out more about the movie by following this link, you can sign the petition here. You can find out more about the different ways that they impact the environment in the following articles: