IRRIGATION engineers meeting at the World Water Forum in Kyoto last week spent a good deal of time insisting that the world鈥檚 use of water could be cut by a fifth or more if farmers irrigated their fields more efficiently. With half the world facing serious water shortages within 20 years, that sounds like a good move. In fact it is a myth, and one that needs to be scotched.
The conventional wisdom runs like this. Two-thirds of the water we use goes to irrigate crops, but less than half of this ever reaches plant roots. The rest runs to waste. So curb the waste, using simple technologies such as more efficient sprinklers, and most of the world鈥檚 water problems could be solved.
The fallacy is that, evaporation aside, most of the water spilt from irrigation schemes is not lost at all. It percolates underground, and from there it is pumped up again by farmers to water the next crop. A waste of energy perhaps, but not a waste of water. Yet most agricultural economists and environment and development lobbyists in Kyoto have not cottoned on to this simple point. As World Bank hydro-geologist Stephen Foster put it: 鈥淭his has the makings of a very dangerous myth.鈥�
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There are, of course, many good reasons for improving irrigation, such as preventing soils becoming waterlogged and saline. But the irrigation engineers across the world who are busily installing more efficient technology are mistaken if they believe that this will mean they can irrigate more fields without draining more water from underground aquifers.
This tale raises two concerns that must be addressed. First, we need a better informed debate among the custodians of the world鈥檚 water. Plenty of people around the world are working on new ideas for how to keep taps running without emptying rivers, how to take away human sewage without polluting the nearest river, how to use wetlands as natural reservoirs and much more (see 鈥淪afe water remains a mirage鈥�). But among those who should be devising strategy there is a chronic lack of direction and intellectual rigour.
Ministers in Kyoto flunked their chance to map out the path for meeting the UN鈥檚 water and sanitation targets and agree on sensible ways to manage the world鈥檚 river basins. Comparing the draft declaration circulated at the start of the conference with the final version, it is hard to see why ministers bothered to show up at all. In fairness, they are badly served by the creaking infrastructure of World Bank economists, officials of high-sounding bodies such as the World Water Council, which put on the meeting, ageing grandees from the heroic days of dam building, and get-rich-quick merchants from the new international water companies.
The second concern centres on groundwater. Despite the billions of dollars being spent on dams, and on canals to channel water from the dams to fields, small farmers increasingly rely on water pumped from beneath their feet. In large parts of the world, underground supplies are a bigger source of water than rivers. Yet while there has been a vigorous debate about the highly visible infrastructure for managing rivers, there is no such discussion on groundwater.
This is doubly distressing, because while the river water we use today will be replenished tomorrow, groundwater we use is gone forever. Much of the water in the great underground reservoirs such as those beneath the Sahara, the north China plain, the Ganges basin and the American high plains is tens of thousands of years old. We are mining some of these reserves hundreds of times faster than they are being replenished.
Then there is pollution. Because nobody bothered to check the chemistry of groundwater before installing pumps, some of it is delivering lethal doses of arsenic and fluoride to unsuspecting people. Worse, much of what is not naturally polluted is being slowly poisoned by pesticides and industrial pollutants washing down from the surface. And as coastal aquifers are pumped out, salty water infiltrates from beneath the sea. It may be decades before we notice the difference in the water from our taps, but by then the wells will have been poisoned for good.
Widespread indifference to the state of the world鈥檚 aquifers was one of the shocks of Kyoto. This vital resource for the future of humanity 鈥� right up there with rainforests, oceans and the air we breathe 鈥� is clearly being abused with reckless abandon.