Environment & Energy

China has announced plans to build the world’s largest hydroelectric project at a remote river gorge in eastern Tibet, an ecological treasure trove close to a disputed border with India. Indian politicians have reacted angrily, saying it gives China the ability to release destructive “water bombs” across the border in any future conflict. They are planning a retaliatory dam on their side of the border that experts say could be at least as environmentally destructive.

Two Chinese dams will barricade the Yarlung Tsangpo, the Tibetan name for the Brahmaputra River, as it is about to flow through the world’s longest and deepest river canyon — think the Grand Canyon on the Colorado River, only three times as deep. Projected to cost $137 billion, the scheme will be the world’s biggest single infrastructure project, with almost three times the generating capacity of the world’s current largest hydroelectric dam, China’s Three Gorges on the Yangtze River.

Chinese ecologists say the canyon is one of the most precious biodiversity hotspots on the planet, containing some of Asia’s tallest and most ancient trees as well as the world’s richest assemblage of large carnivores, especially big cats. But India’s anger is geopolitical. Pema Khandu, the chief minister of Arunachal Pradesh, the Indian state immediately downstream, called the project “a big threat” that could dry up the river through his state during routine operation and potentially be weaponized to unleash a flood in which, he said, hundreds of thousands could lose their lives.

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The project could also impact sediment flows in the river. Erosion in the canyon currently supplies 45 percent of the total volume of sediment that flows downstream on the Brahmaputra, says Robert Wasson, a geomorphologist at James Cook University, in Australia. Bypassing the canyon could reduce sediment supply to the lower reaches and damage the river’s vast delta, says Sahana. “Any disruption to the balance of sediment could accelerate coastal erosion and make the already low-lying [delta] area more vulnerable to sea-level rise.” But this outcome is far from clear, says Wasson, as too little is known about sediment movement on the river. Such impacts would be gradual. But there are also fears of more catastrophic outcomes. The dam site is on a boundary between two major tectonic plates in one of the world’s most seismically active regions. “If I were a Chinese planner, I would be most worried about a great earthquake” that could breach the dam, says Wasson. The strongest earthquake ever recorded on land, the magnitude 8.6 Assam-Tibet quake, happened in 1950 just 300 miles away.

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https://e360.yale.edu/features/china-tibet-yarlung-tsangpo-dam-india-water