More on water:

Asian farmers sucking the continent dry�

A generation ago, Indian farmers in the state of Gujarat used bullocks to lift water from shallow wells in leather buckets. Now they haul it from 300 metres below ground using electric pumps. But that technological revolution is about to have devastating consequences. ...

ndia is at the epicentre of the pump revolution. Using technology adapted from the oil industry, smallholder farmers have drilled 21 million tube wells into the saturated strata beneath their fields.

Every year, farmers bring another million wells into service, most of them outside the control of the state irrigation authorities. The pumps, powered by heavily subsidised electricity, work day and night to irrigate fields of thirsty crops like rice, sugar cane and alfalfa.

But this massive, unregulated expansion of pumps and wells is threatening to suck India dry. "Nobody knows where the tube wells are or who owns them. There is no way anyone can control what happens to them," says Tushaar Shah, head of the International Water Management Institute's groundwater station, based in Gujarat. "When the balloon bursts, untold anarchy will be the lot of rural India," he says. ...

The same revolution is being replicated across Asia, with millions of tube wells pumping up precious underground water reserves in water-stressed countries like Pakistan, Vietnam, and in northern China.

In China's breadbasket, the north China plain, 30 cubic kilometres more water is being pumped to the surface each year by farmers than is replaced by the rain. Groundwater is used to produce 40 per cent of the country's grain, and Chinese officials warned this week that water shortages will soon make the country dependent on grain imports.

Vietnam has quadrupled its number of tube wells in the past decade to one million, and water tables are plunging in the Pakistani state of Punjab, which produces 90 per cent of the country's food. ...

At least a quarter of India's farms are irrigated from over-exploited reserves of water that threaten to run dry in the coming decades, says Shah. Hundreds of millions of Indians may see their land turn to desert. "In some areas accessible groundwater supplies could be exhausted within the next five to 10 years."

It is already happening in the southern state of Tamil Nadu, says Kuppannan Palanisami of Tamil Nadu Agricultural University in Coimbatore. A plunging water table means that only half as much land in the state can be irrigated compared with a decade ago.