A sand dune deployed with sacsaoul fix near the Mogao Grottoes.[Photo provided to China Daily]

Heritage site

Mogao Grottoes, the World Cultural Heritage site a 50-minute drive from Crescent Spring, is on the southeastern edge of the Kumtagh Desert, one of the largest deserts in China, and at the foot of Singing Sands Mountain. The weather is dry, and flying sand, carried along by fierce winds, is a frequent, if not constant, companion. In preserving the 1,600-year-old grottoes, dryness has been an ally, but the wind and sand damage the caves and murals. In fact there in the 1940s the entrance of the caves was buried in sand.

At the entrance of cave No 17 of Mogao Grottoes, guides invite visitors to inspect the scars that sand has left on walls, sand that buried the entrance of the cave completely, too, before the Taoist priest Wang Yuanlu discovered thousands of rolls of Buddhist sutra in the cave in 1900.

"Carried along by the wind are minute sand particles invisible to the naked eye, and these things have sharp corners and edges that cut into the surface of murals, degrading the color," says Zhang Guobin of the Dunhuang Academy, who is in charge of sand control.

On the top of the Mogao Grottoes, wind blows mainly from three directions, northeast, northwest and most frequently south. These winds carry with them sand from Singing Sands Mountain and the nearby Gobi.

After studying the wind conditions and the flow of the moving sand, researchers have taken steps to combat the erosion of wind and sand.

They have built A-shaped sand barriers so sand that northwestlerly winds carries along is blown back by winds from the northeast. This reduces sand moved by northwesterly winds by 95 percent, and sand accumulated at night by 60 per cent.

They have also created a man-made semi-desert, pressing stones of certain sizes into the sand to prevent sand from flying.