Friday, 23 April 2010

There is no such thing as a water shortage

Well, it has been sunny here for several days in a row now, so any time soon we can expect a hosepipe ban.

The idea of a water shortage is crazy when you think about it. Looked at from space, the defining feature of the Earth, when compared with the other planets in our solar system, is water. Our world is blue with the stuff. In round figures there are 1.4 billion cubic kilometres of water on the Earth. This is such a huge amount, it’s difficult to get your head around. A single cubic kilometre (think of it, a cube of water, each side a kilometre long) is 1,000,000,000,000 litres of water.

Divide the amount of water in the world by the number of people and we end up with 0.2 cubic kilometres of water each. More precisely, 212,100,000,000 litres for everyone. If you stack that up in litre containers, the pile would be around 10 million kilometres high. With a reasonable consumption of 5 litres per person per day, the water in the world there shouldn't be a shortage for 116,219,178 years. And that assumes that we totally use up the water. In practice, the water we ‘consume’ soon becomes available again for future use. (If it didn't we'd all blow up like balloons and pop.) So where’s the water shortage?

Things are, of course more complicated than this simplified picture suggests. In practice, we don’t just get through our five litres a day. The typical Western consumer uses between 5,000 and 10,000 litres. In part this happens directly. Some is used in taking a bath, watering the lawn, flushing the toilet – but by far the biggest part of our consumption, vastly outweighing personal use, is the water taken up by manufacturing the goods and food that we consume. Just producing the meat for one hamburger can use 3,000 litres, while amazingly a 1kg jar of coffee will eat up 20,000 litres in its production.

However, even at 10,000 litres a day, we still should have enough to last us over 57,000 years without even reusing any water. So where is the crisis coming from? Although there is plenty of water, most of it is not so easy to access. Some is locked up in ice or underground, but by far the greatest majority – around 97% of the water on the planet – is in the oceans. It’s not particularly difficult to get to, certainly for any country with a coastline, but it is costly to make use of. The fact that an island nation like Britain is prepared to spend huge amounts of money on reservoirs to collect a relatively tiny proportion of fresh water, rather than use the vast quantities of sea that surrounds it, emphasizes just how expensive is the desalination required to turn seawater into drinkable fresh water.

Water shortages, then, come down to a lack of cheap power. There isn't a water shortage, there's a power shortage. Getting more, cheaper, cleaner energy should be a much bigger priority than it seems to be - as so many of the problems the worlds faces are really energy problems in disguise.

Image from Wikipedia
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