Gaw-Lee!! The Economist Discovers Damming Mekong From Tibet To Phnom Penh Might Be Bad Idea!
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A little way downriver, a state-owned power utility is building the 990-megawatt Wunonglong dam. In 1995 the Manwan dam, some 600km farther downstream, became the first to stem the river’s flow. Since then five more dams have been finished along its Chinese reach; the Wunonglong dam is one of a further 14 being planned or built there. China’s Communist Party has long been keen on dams. At least 86,000 have been built over the past six decades, providing 282 gigawatts (GW) of installed hydroelectric capacity by 2014. The government is building yet more to curb the country’s greenhouse-gas emissions. By 2020 it wants an astonishing 350GW of installed hydropower capacity; in the European Union that would be enough to meet about three-quarters of total electricity needs. The dam at Wunonglong, about 300 metres long and more than 100 metres high, will provide a smidgen less than one of those extra gigawatts. The other 13 are expected to add 15.1GW more.
Downriver countries intend to build another 11 large dams on the Mekong, with dozens more planned for its tributaries. In 20 years the Mekong could well be dammed from Tibet to just above Phnom Penh, where the delta begins. In no other large river basin in the world is the planned rate of growth of hydropower as great. The dams will change the quality of the water in the river and the rate at which it flows. Some of this change could be for the better. Dams can prevent flooding by regulating the flow of water downstream. But some Mekong riverbank agriculture would not welcome too steady a flow. Increasing water in the dry season would shrink riverbeds, leaving less space for crops—millions of Mekong-basin dwellers grow vegetables on riverbanks. Reducing water in the rainy season produces smaller floodplains with less sediment deposited in them, impoverishing the soil.
According to International Rivers, an environmental NGO, the full cascade of dams planned for the Lancang would trap nearly all of the sediment coming from China, cutting the water’s sediment load in half. That will be bad for soils and bad for fish; the sediments provide the river’s nutrients. And the dams lower down could worsen the problem; the clear, “hungry” water that flows from them in spates will carry away existing sediment in riverbanks and riverbeds. Some of that will be deposited farther still downstream; some will wash uselessly out to sea.
Those lower dams will also make things yet harder for the nutrient-deprived fish. The 11 proposed in Laos and Cambodia could block the migration of around 70% of the Mekong’s commercial fish catch. Interfering with the fish’s feeding and reproduction to that extent would imperil the food security of populations across the lower Mekong basin, where the average person eats some 60kg of freshwater fish per year, more than 18 times what is on the menu in Europe or America. Considering how poor many of the people here are, replacing fish as a primary protein source is virtually impossible.
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http://www.economist.com/news/essays/21689225-can-one-world-s-great-waterways-survive-its-development
