water > features > growing thirst of an arid earth
Growing thirst of an arid earthPosted: 24 Jul 2006
Thanks to the way we consume water - up to 100 times our weight each day - rivers from the Amazon to the Murray are running dry, writes Fred Pearce
Many of the backwaters and billabongs along the Murray River [in South Australia]have not filled for more than a decade. The gum trees along their banks are dying. Trees that have survived 1000 years, hunkering down during regular dry spells, have no answer to the extended drought in the basin that has resumed again in full force this year.
"It is about 10 years since our trees had a decent drink," South Australia's Minister for the River Murray Karlene Maywald complains.
The Murray is far from alone. From Alabama to Afghanistan, and Italy to Indonesia, journalists are filing stories of failed rains and mighty rivers reduced to a trickle. Nor is this a temporary problem. Across the world some of the greatest rivers - the ones we all remember from geography lessons - have been regularly running dry in recent years. For most of the time, virtually no water reaches the sea from the Yellow River in China, the Indus in Pakistan or the Nile in Egypt.
On the Colorado in the US west, only a trickle of water crosses the border into Mexico these days, and on the Rio Grande in Texas the river is reduced to a series of muddy pools for more than 300km downstream of El Paso. The world's atlases no longer tell the truth.
Even the mighty Amazon, which carries one-fifth of all the water in all the world's rivers, ran low last year. Stories emerged from the Brazilian rainforest last week that low flows are once again revealing sandbanks along the river's upper stretches.
What is going on? Where has this hydrological crisis come from? Climate change is part of the problem. Across the southern half of Australia, there is a clear trend of reduced rains. The pattern goes back three decades and stretches from Perth to Victoria and Tasmania. Meteorologists say the frontal weather systems are tracking farther south, raining over the ocean rather than the land.
This change could be part of a natural cycle. Things could be back to normal next year. But if, as many scientists believe, this is a result of man-made global warming, then the drying is bound to intensify. And other places are showing evidence of prolonged droughts.. In southern Spain and Italy, Sahara-like conditions are crossing the Mediterranean and pushing into Europe. Last year good rains in the US west led many to believe that a decade-long drought had broken. But drought has resumed its grip this year. It's looking as though last year was the exception to a new rule.
Failure of the rains is only part of the problem. Something else is happening, too. Across the world, abstraction of water from rivers is increasing by leaps and bounds. The Murray is running dry in large part because its tributaries are being tapped to water one of the largest irrigated regions. Rice, sugar and cotton farmers are taking prodigious amounts of water from a river system that drains one-seventh of Australia. A single farm, the Cubbie cotton station in southern Queensland, irrigates 200sqkm, taking 150,000 megalitres each year from the Balonne River, a Murray tributary. The station has a reservoir 27km across, large enough to contain the contents of Sydney Harbour.
Government plans to buy Cubbie station and shut it down, as a water conservation measure, have so far come to nothing. But the stakes are high. In central Asia, diversions to cotton farmers have virtually emptied the Aral Sea, once the fourth-largest inland sea. Similarly, the heart of Australia is being sucked dry.
Farming accounts for two-thirds of the water we take from nature worldwide and 85 per cent in Australia. That water is mostly abstracted from rivers but, as they run dry, underground reserves are increasingly being tapped and exhausted. In India, farmers have sunk 20 million tube wells in the past decade to tap underground water. Water tables are sinking fast and researchers recently estimated that farmers are pumping up a staggering 100 cubic kilometres a year more than the rains replace.
The roots of this global crisis go back to the green revolution, the scientific crusade of the 1970s and '80s to produce new high-yielding crop varieties to feed the world's fast-growing population.
Back then, the fear was that billions could be starving by the turn of the millennium. It hasn't happened because the green revolution did its job, but at a cost. While the new crops provided bumper yields, they often made less efficient use of water than the old crops. Two statistics tell that story. The world today grows twice as much food as it did in the '70s, keeping pace with population growth. But to do that we take three times more water from rivers and underground reserves.
Few realise how much water it takes to get through the day. On average, we drink no more than five litres of the stuff. Even after washing and flushing the toilet, filling the swimming pool and hosing the car, Europeans get through only about 150litres each, though an average Australian manages to push that to 350litres a head. That may be profligate. But it is only when we add in the water needed to grow what we eat and drink that our personal water footprint really begins to soar.
According to statistics compiled by the UN's Educational, Scientific and Cultural Organisation,, it takes 2000 to 5000 litres of water to grow 1kg of rice. That is more water than many households use in a week for just a bag of rice. It takes 1000 litres, one tonne of water, to grow 1kg of wheat and 500 litres for 1kg of potatoes.
When you start feeding grain to livestock for animal products such as meat and milk, the numbers become yet more startling. It takes 11,000 litres to grow the feed for enough cow to make a hamburger; and 2000 to 4000 litres for that cow to fill its udders with one litre of milk. If you have a sweet tooth, so much the worse. Every teaspoonful of sugar in your coffee requires 50 cups of water to grow it. Which is a lot, but not as much as the 140 litres of water (or 1120 cups) needed to grow the coffee. Prefer alcohol? A glass of wine or a pint of beer requires about another 250 litres and a glass of brandy afterwards takes a staggering 2000 litres.
We are all used to reading detailed technical information on most food packaging about their nutritional content. Maybe it is time we were given some clues as to how much water it takes to grow and process the food.
It's no wonder international tensions over rivers are growing. When an upstream country can empty a river before it crosses the border, downstream neighbours are understandably concerned. Turkey's dams can dry up the Euphrates before it reaches Syria and Iraq. Israel empties the River Jordan before it reaches the country that bears its name. Egypt says it will take up arms against any upstream neighbour that dares to take the Nile. No wonder people talk of water wars.
Happily, Australia doesn't share a river with anyone. But it is limbering up for its own internal hydrological strife. This week, Maywald complained that irrigators in upstream NSW had been breaching their limits on abstractions of water from the Murray for several years, leaving river flows in South Australia dangerously low. During eight years of drought, the total over-abstraction upstream would have filled most of Adelaide's taps in that time, she says.
What should we do? At a World Water Forum held in Mexico City in March, engineers, politicians and financiers called for investment in more dams and water-abstraction schemes to meet growing demand for water. But what is the point of more dams when the rivers are drying up?
Clearly, there needs to be an engineering rethink. One option is schemes to move water from wetter to drier areas. China is spending $60billion on a vast canal project to pump water from the wet south to the arid north. Australians from time to time discuss huge canals or pipes to bring water south from the rivers of the monsoon lands of the north, such as the Clarence, Daly and Burdekin.
But such schemes are catastrophically expensive and may in any case fall foul of changing climate. Earlier this year, it emerged that one source area for China's south-north scheme is drying up, so the main canal may never fill. And Australian schemes work out more costly than desalinated seawater. Farmers could never afford their product.
But there are better ways. The good news is that we can use our water far more efficiently. Often that can be done locally. Rainwater harvesting is a simple technology, inexplicably forgotten in our modern world of big engineering. But it is catching on again. In India, thousands of farming villages have begun catching the summer monsoon rains and storing the water in ponds and down their wells. Maybe Australian farmers have a thing or two to learn from them.
We also need to recycle water and reduce the rampant waste in most water engineering schemes. Those reservoirs on the cotton farms of Queensland lose up to 40 per cent of their water in a year to evaporation. Lake Nasser, behind Egypt's Aswan High Dam on the Nile, loses more water annually to evaporation than Britain uses in a year.
Millions of farmers worldwide still irrigate their crops by flooding their fields. Most of the water evaporates and little, in practice, reaches the plants. But cheap, modern systems of drip irrigation - delivering water drop by drop close to the crop roots - can cut water demand by 70 per cent or 80 per cent. Many of Australia's hi-tech farms are adopting such systems. But often they are using them to expand their acreage rather than to keep water in the rivers
Scientists say we need a blue revolution to breed crops that use water better and to train farmers to use water more sparingly. They are working on it. Of course we will all have to join in to save water as best we can, turning off taps, fixing leaks, watering plants at night, sparing the toilet flush sometimes.
But wait a moment before you log on to buy one of those jokey T-shirts advertised on the internet with slogans such as Save Water, Bathe With a Friend. Good message, but you could fill roughly 25 bathtubs with the water needed to grow the cotton needed to make the shirt.
Source: This article first appeared in The Australian on 23 July 2006