When Rivers Run Dry

By Fred Pearce

British environmental writer Fred Pearce considers a looming water crisis linked to increased agricultural production, what he describes in his book, When the Rivers Run Dry, as "the defining crisis of the 21st century."

photo The almost dry Yan River in Yan'an; Northwestern China faces severe water shortages due to overuse and pollution of its already limited supply  [Qilai Shen/Panos Pictures]

Few of us realize how much water it takes to get us through the day. On average, people in developed countries drink about 5 liters. Even after washing and flushing the toilet we get through only around 150 liters each. But when we add in the water needed to grow what we eat and drink, the numbers really begin to soar.

It takes between 2,000 and 5,000 liters of water to grow a kilo of rice. That is more water than many households use in a week. It takes 1,000 liters to grow a kilo of wheat, and 500 liters for a kilo of potatoes. It takes 11,000 liters to grow the feed needed to produce enough meat for one hamburger, and between 2,000 and 4,000 liters to fill a cow's udders with just 1 liter of milk.

In this way, an average Western consumer gets through 100 times his or her own weight in water every day--more than 2,500 cubic meters (or 2,500 tons) a year. How does that match up to supply?

Most of our water comes from rivers--the only truly renewable source, since the rivers are constantly refilled by rainfall. Hydrologists reckon there are 9,000 cubic kilometers flowing down accessible rivers every year. Divide that up among the world's population, and you come up with 1,400 cubic meters of water each.

So: supply 1,400 cubic meters per head; demand, if everyone wants to live like a Westerner, 2,500 cubic meters. We have a problem. Amazingly, we are running out of freshwater.

And that is why some of the great rivers of the world like the Yellow River in China, the Nile in Africa, the Indus in Pakistan and the Colorado in the U.S. often don't reach the sea any more. And why we are living on borrowed time and borrowed water--keeping India fed by pumping out its underground water reserves twice as fast as the monsoon rains can replace them, for instance.

Virtual Water

How did we reach this point? A generation ago, the world faced a challenge rather like climate change today: how to feed a world population set to double in 30 years. We did it, thanks to new crops that delivered more yield for every hectare of land. But unfortunately those "green revolution" crops are very thirsty, and often produce less "crop per drop" than the varieties they replaced. Today we grow twice as much food, but use three times as much water to do it. We thought we were going to run out of land; actually we are running out of water.

As countries dry up, they start to import food. China is at that point right now. India will be next. In fact, you can look at the world trade in food as a surrogate trade in the water used to grow it--virtual water, economists call it. That is why recent droughts in Australia, coupled with the rising demand for food in parched China, are causing food shortages and price rises worldwide.

This is likely to get worse. And the demands of biofuels and the disruption of supply likely due to climate change are only going to make things worse.

Nobody will be immune. Britain doesn't think it has a water problem. But it imports something like 40 cubic kilometers of virtual water a year in the form of crops. We would be in serious trouble if we tried to find all the water we needed to grow our own food within our own borders.

Incidentally, it is worth emphasizing that the world's requirements for water for drinking and other domestic uses are trivial compared to the use for farming. Providing clean drinking water is very rarely a matter of absolute water shortages, and usually much more about basic infrastructure.

photo A water jet irrigates a potato field in France; increased agricultural production is straining the world's water supplies  [Fernand Ivaidi/Getty Images]

What do we do? Some see desalination of seawater as the ultimate solution. For coastal regions in rich countries, it is certainly an option. But it remains too expensive for agriculture. And desalination consumes large amounts of energy.

Engineers, politicians and financiers, including the World Bank, still see the solution in more large dams to catch more water. Sometimes that can be helpful. But what is the point of more dams when the rivers are already drying up? A global study published in 2007 by the International Water Management Institute in Colombo, Sri Lanka, showed that a quarter of the world's population live in areas where the water is already fully allocated. New developments in these areas will only take water from some users and give it to others.

A Search for Solutions

If many rivers are already exploited to their limit, what else can be done? Moving water around is possible--but again very expensive. China is currently spending $60 billion on a series of canals to pump water from the wet south to the arid north. India is talking about trunking water from the great monsoon rivers of the north, like the Ganges, to the dry south and west. But the price tag for construction alone is $200 billion. All this could be good business for engineers, but rarely of help to farmers.

Two big things need to happen. First we need to get better at catching the rain where it falls and before it disperses. We need a modern version of the old water butt catching rainfall off the roof for use in the garden.

In villages across India and China, people are reviving ancient methods of capturing the monsoon rain as it falls, and often pouring it down their wells to be saved for the dry season. This is more efficient and much cheaper than allowing the water to run off the fields and into rivers, to be collected behind some distant dam and then pumped back up to the villages again. Local control wastes less water and encourages farmers to manage their water better, and save it for their own uses.

But we also need a massive revolution in the way we use water. Luckily there are huge gains to be made here. And agriculture, as the biggest user of water, especially in the driest countries, can contribute the most.

Tens of 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 systems of drip irrigation--delivering water drop by drop close to the crop roots--can cut water demand by 70 or 80 percent.

This needn't be high-tech. In India farmers have developed their own indigenous system using perforated strips of plastic tubing sold widely to hold iced lollies. They take the rolls of tubing, known locally as Pepcees, and lay them out on their fields. When they connect the tube to a tap, the water drips out through the perforations. The result is drip irrigation, virtually free.

I am both a pessimist and an optimist about water. A pessimist because we often use water so wastefully. But an optimist because I can see that we could do things so very much better.

Water is a resource like no other. It is a commodity but also a human right. We have somehow to ensure universal access, while encouraging communal efforts at conservation and price incentives to encourage more efficient use. It is a tough task, combining all these things.

Water, they say, is the new oil; it will be the cause of water wars in the 21st century. Maybe so. But it is more than that. We could manage without oil--but none of us, for even one day, can manage without water.


Fred Pearce, a British journalist and senior environment consultant of New Scientist magazine, has reported on environment and development issues for over 20 years. His book When the Rivers Run Dry on the emerging global water crisis is published by Eden Project Books. His latest book is Confessions of an Eco-Sinner.