Nor Any Drop To Drink
This week's New Scientist also has an article on the latest in mega-engineering trends, the same trend that Mapchic wrote about recently on Geographica: dirty great big dams. New Scientist refers to them as "megawater" projects. And the Three Gorges Dam that Mapchic spoke of is only the beginning. Try this for size:
The third, western, arm is the biggest and most complex. It will capture the headwaters of the Yangtze in a 300-metre-high dam [That's as tall as an 80-storey building. — Pixy] downstream from the melting glaciers of Tibet. Every year, it will lift a volume of water equivalent to a quaerter of the annual flow of the river Nile through a 100-kilometre tunnel into the upper reaches of the Yellow river.The article gives some grim statistics on just why China feels forced to undertake such huge projects:
Five times in the last decade, the Yellow river has failed to reach the sea for part of the year because every drop of water has been diverted.The north of China, the article tells us, has two thirds of the nation's farmland and only one fifth the water; in the south the figures are reversed. So there are sound reasons for these projects, but the history of similar works - the Aswan Dam beaing a prime example - raise doubts about their long-term prospects. The article also refers to an (admittedly speculative) Australian plan to "drought-proof" the country by diverting northern rivers such as the Clarence (which is actually in the southern half of Australia) and the Ord, inland in the general direction of Adelaide. Now, I'll grant that Adelaide needs all the water it can get, but the problem with trying to drought-proof Australia is that it's a frigging desert. Ahem. Sorry. It's not a question of there being more water than needed in some places and a shortage in others, as in China; even in principle there's not enough water to go around. The recent drought affected pretty much the entire country; in Sydney, which is where it is because of the high local rainfall (and the harbour, of course), it didn't rain at all for months. If you want to drought-proof Australia, you have two choices: either fix the world in a permanent La Niña cycle (perhaps by dropping enormous ice cubes in the Pacific) - which really doesn't do that much and will probably piss off every country in the world except Australia - or increase the water supply in the interior of the continent, perhaps by building a mountain range stretching from Ayers Rock to Adelaide. This idea (which was actually floated about twenty years ago) would give real meaning to the term mega-engineering.
The aquifers [underground water] of northern China are being depleted by a staggering 30 cubic kilometres a year.
The water table beneath Beijing has fallen 59 metres in the past 40 years.
Posted by: Pixy Misa at 11:46 PM
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