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"It is really quite amazing by what margins competent but conservative scientists and engineers can miss the mark, when they start with the preconceived idea that what they are investigating is impossible. When this happens, the most well-informed men become blinded by their prejudices and are unable to see what lies directly ahead of them. "

Arthur C. Clarke - Science Writer

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.

So much water is being drawn from underground reserves that they, and the pumps they feed, are running dry, turning fields that have been fecund for generations into desert.

The world's leading water scientists warned this week that this little-heralded crisis is repeating itself across Asia, and could cause widespread famines in the decades to come.

Day and night
 

India 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.

Shah gave his apocalyptic warning at the annual Stockholm Water Symposium in Sweden last week. His research suggests that the pumps, which transformed Indian farming, bring 200 cubic kilometres of water to the surface each year. But only a fraction of that is replaced by the monsoon rains.

China's breadbasket
 

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.

In India, more farmers now provide their own water via wells and pumps than rely on the government's irrigation system, which is based on a network of canals. Corrupt management, low investment and drying rivers have made the national system increasingly decrepit, and it rarely delivers water to farmers when they need it.

In contrast, the $600 pumps are bringing short-term prosperity to much of the country, turning India from a land of famine to a major rice exporter in less than a generation.

Indian farmers have invested some $12 billion in the new pumps, but they constantly have to drill deeper to keep pace with falling water tables. Meanwhile, half of India's traditional hand-dug wells and millions of shallower tube wells have already dried up, bringing a spate of suicides among those who rely on them. Electricity blackouts are reaching epidemic proportions in states where half of the electricity is used to pump water from depths of up to a kilometre.

Plunging water table
 

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.

Large-scale farmers with powerful pumps and deep wells still get good prices growing water-hungry crops like sugar cane and bananas, but 95 per cent of the wells owned by small farmers have dried up, Palanisami says. Some villages now stand empty.

Another crisis hotspot is northern Gujarat, where water tables are dropping by 6 metres or more each year, according to Rajiv Gupta, a state water official.

Is there a way out of the crisis? Some states are placing thousands of small dams across river beds in a bid to replenish groundwater by infiltration. And Hindu water priests are organising farmers to capture the monsoon rains in ponds, in the hope that water will infiltrate and recharge the aquifers.

The last Indian government proposed a massive $200 billion River Interlinking Project designed to redistribute water around the country. But the new government elected earlier this year has gone cool on the idea. In any case, the water supplied would probably come too late.