Melting glaciers in China’s Qilian mountains could create long-term water shortages, scientists say.

Researchers say the largest glacier in the 800-kilometre mountain chain on the north-eastern edge of the Tibetan plateau has retreated about 450 metres in recent decades.

The 20-square kilometre glacier, Laohugou No. 12, has shrunk by about 7 per cent since measurements began since the 1950s.

The melting is accelerating, scientists say, and losing thickness as well.

“The speed that this glacier has been shrinking is really shocking,” says Qin Xiang, the director at the glacier’s monitoring station.

Since the 1950s, average temperatures have risen by around 1.5℃, Qin said.

The glacier retreat was 50 per cent faster from 1990 to 2010 than it was from 1956 to 1990, according to the China Academy of Sciences.

They have also found that the flow of water in a stream near where the Laohugou No. 12 ends is about double what it was 60 years ago.

Further downstream, near Dunhuang, water has formed a lake in the desert for the first time in 300 years, state media reports say.

“Across the region, glacial melt water is pooling into lakes and causing devastating floods,” said Greenpeace East Asia climate and energy campaigner Liu Junyan.

“In spring, we're seeing increased flooding, and then when water is needed most for irrigation later in the summer, we're seeing shortages.”

Farmers say they have not been able to water their crops over two crucial summer months.

The China Academy of Sciences expects melting in the mountains will peak within a decade, causing snow melt to decrease due to the smaller glaciers, which could bring water crises.