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Vast water supplies hidden under N. China desert
(Agencies)
Updated: 2004-11-25 09:40

A desert in China's Inner Mongolia that has the highest sand dunes in the world holds a vast store of underground water which, if used wisely, could ease the chronic water shortage afflicting the north of the country, a study says.

Scientists based in China, Australia and Britain scratched just 20 centimetres below the surface of the dunes in the Badain Jaran desert, in western Inner Mongolia, and were stunned to find abundant moisture.

The discovery explains how these dunes, at up to 500 metres (1,625 feet) tall the highest in the world, can survive bone-dry, windy conditions.

"This water is likely to be acting as a cohesion agent, providing the dunes with resistance against wind erosion and transportation," the scientists write in the British weekly journal Nature on Thursday.

Badain Jaran has just 40 millimetres of rainfall (1.6 inches) a year, but evaporation from the dune is five times that amount.

The researchers say the source for the replenishment comes not from the 72 lakes that dot Badain Jaran's unique landscape.

The evidence is that it comes from snowmelt on Qilian Mountain, which lies 500 kilometers (300 miles) away to the southwest.

This precious water percolates through faults in the mountain's rocky roots and then seeps through deep carbonate layers, eventually reaching the dunes and the lakes.

According to their calculation, 500 million cubic metres (17.5 billion cubic feet) could be extracted from the desert groundwater every year.

That would make it a cheaper and more practical alternative to a proposed water-diversion project in areas north of Qilian Mountain, costing 500 million dollars, that would have an annual capacity of 25 million cubic metres (87.5 billion cubic feet).

The team, led by Ling Li at the University of Queensland and China's Hohai University in Nanjing, caution that the extraction would have to be done on a sustainable basis.

"Any resulting dune mobilisation could severely affect the regional eco-environment," they warn.

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