Chinese engineers are testing techniques that could be used to build a 1,000km tunnel – the world’s longest – to carry water from Tibet to Xinjiang, experts involved in the project say.
The researchers estimated the tunnel would be able to carry 10 billion to 15 billion tonnes of water from the Yarlung Tsangpo River to the Taklimakan Desert each year. That’s about a quarter of the annual flow of the Yellow River, the second longest river in China and the cradle of Chinese civilization.
Each kilometer of tunnel would cost at least one billion yuan due to the difficult terrain and taxing altitude of the Tibetan Plateau. The $1 trillion yuan cost would be about USD150 billion.
The water shortage in Xinjiang was in many ways similar to that in California early in the 20th century. The Central Valley Project, devised in 1933, diverted water from northern California to the San Joaquin Valley, turning it into the world’s most productive agricultural region.
The proposed tunnel, which would drop down from the world’s highest plateau in multiple sections connected by waterfalls, would “turn Xinjiang into California”, one geotechnical engineer said.
The Chinese government started building a tunnel in the centre of Yunnan province in August that will be more than 600km long, local media reported. Comprising more than 60 sections, each wide enough to accommodate two high-speed trains, it will pass through mountains several thousand meters above sea level in an area plagued by unstable geological conditions.
The Tibetan Plateau stops the rain-laden Indian Ocean monsoon from reaching Xinjiang, with the Gobi Desert in the north and the Taklimakan Desert in the south leaving more than 90 per cent of the region unsuitable for human settlement.
However, the Taklimakan sits right at the foot of the Tibetan Plateau, which is known as the water tower of Asia. The more than 400 billion tonnes of water it releases each year – almost enough to fill Lake Erie in the United States – also feeds the source of other major rivers, including the Yellow, Yangtze, Mekong (known in China as the Lancang) and the Ganges.
The Yunnan-Guizhou Plateau in southwest China is, like the Tibetan Plateau, an earthquake-prone zone with many active faults.
Huge hidden ocean under Xinjiang’s Tarim basin larger than all Great Lakes combined.
“Fault zones are our biggest headache,” Zhang said. “If we can secure a solution, it will help us get rid of the main engineering obstacles to getting water from Tibet to Xinjiang.”
The solution they came up with was inspired by subway trains, whose carriages are connected by elastic joints. In the tunnel, Zhang said, flexible materials that were also waterproof and strong would be used to bind concrete pipes together when they passed through fault zones.
The Yunnan tunnel and support facilities will take eight years to build at an estimated cost of 78 billion yuan (US$11.7 billion). It will carry more than three billion tonnes of water each year from northwestern Yunnan to the province’s dry centre and directly benefit more than 11 million people, according to the provincial government.