Hydroelectric power is often promoted as green energy, yet dams, especially in the tropics, can be significant sources of greenhouse gas emissions. When built, reservoirs trap vegetation, which, as it rots, emits both methane and carbon into the atmosphere. A new study in Science of the Total Environment found that a dam in Lao PDR remained a significant source of greenhouse gas emission even a decade after construction. According to the study, the Nam Leuk Reservoir emits between 1.2 and 3.2 gigagrams of carbon annually, an amount comparable to other dam reservoirs in the tropics.
Looking at another reservoir in Lao PDR, however, the study found that distance from construction likely makes a difference in greenhouse gas emissions. Built in 1971—four decades old, instead of onev—the Nam Ngum Reservoir is no longer a source of carbon in the atmosphere, but carbon a sink.
The study further notes that clearing vegetation prior to impounding a reservoir may make little difference in resulting carbon emissions, since vegetation around Nam Leuk was partially cleared and burned, yet the dam still emits significant greenhouse gases.
Currently there is a rush of dam building both in Southeast Asia and South America.
CITATION: Vincent Chanudet, Stéphane Descloux, Atle Harby, Håkon Sundt, Bjørn Henrik Hansen, Odd Brakstad, Dominique Serça, Frédéric Guerin. Gross CO2 and CH4 emissions from the Nam Ngum and Nam Leuk sub-tropical reservoirs in Lao PDR. Science of The Total Environment. Volume 409, Issue 24, 15 November 2011, Pages 5382-5391.
Occupy Belo Monte: indigenous stage “permanent” protest against Amazon dam in Brazil
(10/27/2011) Hundreds of people are participating in a protest against the controversial Belo Monte dam in Altamira, Brazil, reports Amazon Watch.
Public opposition pushes Myanmar to suspend giant Chinese dam
(10/04/2011) Large-scale opposition has pushed the Myanmar government to suspend construction of a massive Chinese dam. Being built on the confluence of the Mayhka amd Malihka rivers at the head of Irrawaddy River, the Myitsone Dam would have created a reservoir the size of Singapore and has already pushed 12,000 people off their land. China Power Investment Corporation, which is building the dam, has fired back at the Myanmar government saying their decision will lead to ‘a series of legal issue’.
Last chance to see: the Amazon’s Xingu River
(06/15/2011) Not far from where the great Amazon River drains into the Atlantic, it splits off into a wide tributary, at first a fat vertical lake that, when viewed from satellite, eventually slims down to a wild scrawl through the dark green of the Amazon. In all, this tributary races almost completely southward through the Brazilian Amazon for 1,230 miles (1,979 kilometers)—nearly as long as the Colorado River—until it peters out in the savannah of Mato Grosso. Called home by diverse indigenous tribes and unique species, this is the Xingu River.