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.