New Delhi: Hydropower is usually considered a clean energy source but a latest study has now held that hydropower in Mekong River Basin, the longest river in Southeast Asia, might not be climate friendly and has emissions equalling that from fossil fuel sources.
The finding could be significant for a country like India which at present is considering classifying large hydropower projects as renewable energy projects.
Mekong River is also the seventh-longest in Asia and the 12th-longest in the world. It originates in China, and flows through countries including Myanmar, Laos, Thailand, Cambodia and Vietnam before falling into South China Sea, covering over 3,000 miles.
The study was published in Environmental Research Letters journal on 1 March.
Noting that the Mekong River basin is undergoing extensive hydropower development, the study estimated the emissions of greenhouse gases (GHG) of 141 existing and planned reservoirs using statistical global emission models, with focus on gross carbon dioxide and methane emissions through the reservoir water surface.
The emissions were estimated using statistical models that are based on global emission measurements and the results showed “considerable variation in the estimated hydropower emissions”.
“Altogether, 82% of hydropower reservoirs (119) and 45% of reservoirs facilitating also irrigation (22) have emissions comparable to other renewable energy sources, while the rest have higher emissions equalling even the emissions from fossil fuel power plants. Several of these high-emission reservoirs are still in the planning phase,” said the study.
It pointed out that the results further show that the total basin-wide emissions of hydropower development are considerable.
“Our findings indicate that, although the reservoir emissions per produced energy may be low in the Mekong, hydropower cannot be considered categorically as low-emission energy. The emissions can reach the emission levels from fossil fuels power plants, depending on the characteristics and location of the hydropower project,” the study said.
The study said that “high emissions were related most strongly to low area-to-electricity ratios, large reservoir surface areas and high air temperature” and “therefore each hydropower project should be carefully analysed for its GHG emissions”.
“It is also obvious that careful removal of vegetation and other easily degradable organic matter from the inundated area of a reservoir is fundamental in minimizing GHG emissions from it,” it added.
The study, however, cautioned that its findings should be considered as tentative, given that they are based on global models with high uncertainty.