The Yarlung Tsangpo is the longest river in Tibet. And the Yarlung Tsangpo valley in southern Tibet is the world’s deepest valley with a 7,000-metre (23,000-foot) drop from the highest mountain peak to the lowest basin.
China plans to build a hydropower plant in the valley with electricity generation capacity reaching 70 gigawatts, about three times that of the Three Gorges Dam. The project was approved by the central government last year and included in the 14th five-year plan with a deadline of 2035.
But an icy obstacle could put a halt to much of the plan.
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In 2018, a landslide caused by a melting glacier blocked the Yarlung Tsangpo – the upper stream of the Brahmaputra River – at the Sedongpu Basin in Milin county. It formed a lake containing about 600 million cubic metres of water. With the river spilling over the top at present, the dam could collapse at any time.
The Sedongpu lake sits just a few dozen kilometres upstream from the planned construction site of the super hydropower plant. With so much water hanging overhead, no construction workers can move in to clear the ground.
To build the big dam, they must get rid of the small dam formed by the landslide first.
Several teams of scientists and engineers have flown to Sedongpu in recent years, including some of the nation’s top experts in civil engineering, glacier study and landslide prevention. They collected a large amount of data on the site using drones and other advanced equipment and were asked by authorities to come up with a solution after finishing their assessment.
“The situation is very difficult. There is not an immediate solution yet,” said Xing Aiguo, a professor of civil engineering at the Shanghai Jiao Tong University who was involved in one of the studies.
The experts could not find a way to strengthen the landslide dam or remove it safely. Worse still, they found similar disasters would likely happen again in the same area, thanks to climate change.
“The area is large and there are many glaciers,” Xing said. Even if there is a method, treating such a harsh natural landscape with engineering methods could be technically challenging and costly, he said.
A quarter of the glaciers on the Tibetan Plateau have disappeared since the 1970s, and two-thirds of the remaining will be gone by the end of the century, according to an estimate by the United Nations’ Intergovernmental Panel on Climate Change.
Studies have found that increased meltwater and rising temperatures could make the “roof of the world” more habitable with greater crop yields and advancing tree lines, but the risk of natural disasters, including flooding and landslides, also increased.
And ice could turn a landslide into something more destructive. At Sedongpu, for instance, the icy debris travelled more than 10km (6.2 miles) with a top speed of 72km/h (45mph), according to an estimate by Tibet autonomous region’s geological environmental monitoring station.
The icy material also loosened the landslide dam and made it more prone to collapse. The sheer drop in elevation means even a relatively small amount of water could cause serious destruction downstream.
Liu Chuanzheng, a government researcher with the Consultative Centre of Geohazard Mitigation under the Ministry of Natural Resources in Beijing, said human activity in the Sedongpu area “should be avoided altogether”.
“The development and utilisation of natural resources and energy in the Yarlung Tsangpo river must fully consider the situation of avalanches and debris flows in the Sedongpu valley,” he said in an official report about the landslide published in the journal Geology in China in 2019.
Some Chinese scientists have proposed that instead of building a super dam, a 16km-long tunnel could be dug through one of the high mountains in the Yarlung Tsangpo valley. The water could be directed into the tunnel to push electricity generating turbines. This scheme would reduce the power output to 50GW – or about twice that of the Three Gorges Dam – but reduce the risk of damage from landslides or other natural disasters.
China’s plan to dam the Yarlung Tsangpo has drawn protests from India, which sits directly downstream. A large area in southern Tibet remained disputed by China and India and the latter worried China would use the dam to cut off India’s much-needed water supply.
As a countermeasure, the Indian government plans to build a 10GW dam in its controlled area as well. Indian scientists have told local media the environmental cost of the “dam-for-dam” response in the region would be extremely high and the Indian government should wait until it became clearer what their Chinese counterparts would do before taking any action.
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