Wednesday, April 26, 2006

When the Rivers Run Dry has a (long) interview with British science journalist Fred Pearce, former editor of New Scientist and author of When the Rivers Run Dry, a global investigation into water use and abuse.

Some (edited) excerpts:

"Many countries have run out of water for growing their own crops and are now importing water in the form of food. Egypt really, for instance, lost the ability to feed itself perhaps 30 years ago. It now imports a large amount of water in the form of food. That is the only way it can do it. Water is pretty heavy stuff to move, but the trade in products produced with water is huge, and in many ways can be seen as a trade in water.

"Many large engineering projects suffer from a huge range of inefficiencies. The evaporation from the reservoir behind the Aswan High Dam in Egypt annually amounts to, in metric, 15 cubic kilometres of water [3.6 cubic miles]… that is roughly the amount of water that is used by the whole of the United Kingdom in a year. In other words, you could fill every tap, meet every water demand in the U.K., a country of more than 50 million people, simply by the water that evaporates from the surface behind the Aswan Dam.

"One of the most heartening trends I've seen traveling around the world -- and I've seen it in China and India and in other places -- is the effort by farmers and villagers to harvest the rain as it falls. They don't let the water go into the rivers and run away to perhaps a large dam, or run away to the sea. They simply capture it locally, and even pour it back down their wells, creating a storage system so that they can pump it up later in the year.

"Domestically, American users are among the highest water users in the world, but [Americans] stabilised water consumption in recent years, principally by having more efficient toilets that use much less water in the flush. Canadians have not changed their toilets in the same way. They are probably now the No. 1 domestic users of water in individual homes. But neither the U.S. nor Canada reaches anything like the per capita water consumption of Uzbekistan and Turkmenistan.

"Both of those use absolutely vast amounts of water to irrigate their cotton crops. It's a system set up by the Soviet Union, which has been carried on through today. They produce huge amounts of cotton grown using water taken out of the rivers in what is in many ways an arid region. The main consequence of that huge use of water is that they've dried up the Aral Sea, which was once the fourth biggest inland sea. It's sitting in Central Asia not far from the Caspian Sea, which is even bigger. They dried up the rivers that fed that sea, virtually no water reaches the sea anymore, and the sea has retreated fantastically.

"Nobody knows exactly what is going to happen to rainfall under global warming. We're fairly certain that climate change will make most of the world warmer. There are uncertainties about how weather systems are going to change, but the bottom line probably is that the wet places will get wetter, and the places that are dry will get still drier."

Fascinating fact to throw into a lagging conversation: It takes 40 gallons of water to grow the ingredients for the bread in a single sandwich. 265 gallons to produce a glass of milk. 800 gallons for a hamburger.

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