Gasping for a virtual drink

… Most crops take extraordinary amounts of water to grow: a thousand tonnes for a tonne of wheat, for instance. In fact, two-thirds of all the water abstracted from the world’s rivers and underground reserves goes for crop irrigation. Unsurprisingly, dry countries, like most of the Middle East, don’t have enough water to feed their growing populations.

So they import water. They import virtual water. This trade is huge, the equivalent of 20 times the flow of the world’s longest river, the Nile. Without it, hundreds of millions would starve. But the trade is in trouble.

The world’s biggest supplier of virtual water is, or was until a couple of years ago, Australia. It exported 70 cubic kilometres of virtual water, in the form of fruit and crops, a year. That’s 70 billion tonnes, if you can imagine that better.

Then came drought, which has more than halved that figure. Australia’s wheat exports are down 60%, its rice exports down 90%. The US, the second biggest virtual water exporter, has been diverting much of its water to growing corn for biofuels and hence has been reducing its own exports.

Meanwhile global demand for virtual water is soaring, especially from China, where water is the main constraint on food production. China has effectively run out of water in its traditional breadbasket region in the north of the country, where the Yellow River now rarely reaches the sea in any volume. China can’t feed itself any more.

New Scientist