"It definitely rained the year before that," he added, sounding a little more certain.

Water -- or rather lack of it -- has shaped Wang's life, living as he does in one of China's most arid regions, where sand dunes lap at fields and dust storms regularly harry its people.

When he was a small boy, his family gave up the struggle of trying to eke crops from the stony, dusty soil and moved from their farm in the even drier southern part of Ningxia to the regional capital, Yinchuan.

Since then, Wang, 23, has worked as a coal miner, a building site labourer and as a long-distance truck driver. He does not plan to return to the old family farm.

"My grandparents say it used to be much greener before. They say it once rained for an entire week," he said, looking out from the barren Helan mountains outside of Yinchuan at the desert, pitted with dried up river beds and abandoned fields.

But Ningxia is just part of a wider problem -- China is running out of water.

The figures are stark.

Per capita water resources in the world's most populous country are less than a third of the global average, and falling.

More than 300 million people in rural areas lack clean drinking water, and many are being slowly poisoned by water that contains too much fluorine, salt and even arsenic.

UNBEARABLE STRAIN

Tackling these issues is a key part of Beijing's economic and social development plan for the next five years, but the problems are deep-rooted.

More than a decade of near double-digit economic growth coupled with a still expanding population has put an almost unbearable strain on water demand in China.

Pollution is so severe the Ministry of Water Resources estimates 40 percent of water in the country's 1,300 or so major rivers is fit only for industrial or agricultural use.

"The Rhine and the Thames became cesspools during industrialisation but China's industrialisation is moving so quickly now that it's going to take a gigantic effort to address this," said Dermot O'Gorman, the WWF's China representative.

"The negative effects of pollution and the health effects of dirty drinking water can undermine the development on which you depend," he told Reuters.

China's water is also unevenly distributed, and flooding causes serious damage every year in central and southern China.

To address this and help alleviate drought in the north, the government is spending almost 500 billion yuan (US$62.29 billion) on a diversion scheme to ship the water north.

One of the rivers to benefit from this plan is the Yellow River, the country's longest and once known as "China's sorrow", for the millions of flood deaths it once inflicted.

The Yellow River today is a shadow of its former self, hit by massive extraction of water for farming and industrial use and declining levels of rainfall. In some years, the river runs dry before reaching the sea.

Ill-conceived irrigation has made matters worse. In arid Ningxia, rice is grown beside the river.

"It's probably the craziest place to grow rice. Look at the evaporation in the summer -- it's 40 degrees Celsius and doesn't see rain for months," said Vaclav Smil, a professor at Canada's University of Manitoba and a Chinese water expert.

"The rational thing would be to shut it down and walk away from it, but now you have all these people depending on it," he told Reuters.

"What would you do with these people? Where would you shove them? Gansu? It would be the same," Smil said, referring to Ningxia's equally dry neighbouring province.

SHIFTING SANDS

The prolonged drought has forced Lao Tian to look for alternative forms of work -- sifting for sand to build a new mosque in Xiaokouzi hamlet, in the hills overlooking Yinchuan.