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 20cm 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 500m 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 wrote in the British weekly journal Nature yesterday.
Badain Jaran has just 40mm of rainfall 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 500km 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 meters could be extracted from the desert ground-water 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 US$500 million, that would have an annual capacity of 25 million cubic meters.
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 mobilization could severely affect the regional eco-environment," they said.