The government of China has green-lighted a controversial plan to build a dam across the Yarlung Tsangpo, one of the world's most powerful river drainages. If constructed, it would be the most expensive single infrastructure project of any kind in history, and would outstrip the generating capacity of China's famous Three Gorges Dam.
The Yarlung Tsangpo is one of the world's wildest and most inaccessible stretches of river. It drains the north slope of the Himalayas, and its eastern end is a twisting gorge with three-mile-high walls - the deepest and least-visited river canyon on earth. This stretch of the river is a flood of roiling whitewater, and has never been fully traversed by human navigators from end to end (though some have died in the attempt). The gorge inscribes a curving 180-degree arc through the mountain range, plunging about 6,500 feet to the plains of the Indian subcontinent.
Courtesy NASdA
China's plan to install a dam on this river has been on the table for decades, and it received official approval in the 14th five-year plan. But it involves considerable technical risk. Sitting in the middle of the Himalayan escarpment, it is on an active fault line, and earthquakes above magnitude 4.5 occur in the region about 30 times a year. The largest earthquake ever recorded on land, the 8.6 magnitude Assam quake of 1950, had an epicenter 100 miles away to the southeast. This quake was a powerful enough event to send an entire village sliding into the Yarlung Tsangpo.
The Chinese plan to tame the river is ambitious and complex. After solving the project's significant access challenges, the engineers will have to bore four to six tunnels through the base of a 25,000-foot-tall mountain, Namcha Barwa. The dam on the upper side of the gorge would divert water into the tunnels, "short-circuiting" the Great Bend of the Yarlung Tsangpo and sending half of its flow under the mountain. After a drop of 6,500 feet, the water would flow through hydropower generators with tremendous force, then would reenter the run of the river.
If built, this megadam could generate up to 300 billion kilowatt-hours of power every year - enough to run about seven percent of the entire U.S. electrical grid. By capacity it would outstrip the giant Three Gorges Dam by a factor of three, making it the largest electrical power plant of any kind. At a cost of at least $137 billion, it would also be the world's most expensive single infrastructure project.
Wary neighbors
In India, the Yarlung Tsangpo is known as the Brahmaputra, and Indian leaders are concerned at the possibility of China taking control of the flow of the upper river. Any reduction in water discharge or silt could have an impact on Indian agricultural interests, from Arunachal Pradesh (where India has a border dispute with China) down to the Bangladeshi border.
"The monstrous dam China plans to build on Yarlung Tsangpo will surely lessen the flow of water into India," the Bharatiya Janata Party's Anurachal Pradesh head Tapir Gao told the Deccan Herald. "It is going to spell disaster not only for the northeastern region of India but also for Bangladesh."
