Blue Gold

The Yangtze River flows through China like an arteryA major blood vessel carrying oxygenated blood to the limbs. Metaphorically, any transit route that's vital to the life of an area or nation.. Measuring 4000 miles from the Tibetan Plateau to the East China Sea, it supports the livelihoods of 400 million people.

This year, however, it's running dry. Following the worst rainfall in 50 years, the river has shrunk to a fraction of its usual size. Irrigation canals are empty. Thousands of ships lie abandoned on the exposed mud.

In response, the Chinese government has released billions of cubic metres of water from the vast reservoir that lies behind the famous Three Gorges Dam. The world's largest hydroelectric plantHydroelectric plants store water behind huge dams. The build up of pressure then forces water through spinning turbines which generate electricity., it blocks the river behind a huge wall of concrete, creating an artificial lake the length of Britain.

In normal times, the stored water generates four times more energy than even the biggest nuclear power stations. That energy production has been sacrificed to avert an agricultural and environmental crisis.

But the crisis exposes a fundamental problem, which affects not just China but the whole world: there are too many people and not enough water.

In the last 50 years, the world's population has doubled, to nearly seven billion. By the year 2050, it will have hit nine billion. These billions are eating more, drinking more and consuming more manufactured goods than their ancestors ever did. All of this uses up more water.

Although we think of water as an endless resource, it's not. Many crucial food-growing areas around the world are suffering long-term water shortages.

New deserts have appeared in Mongolia and Africa as humans drain rivers dry.

In India, farmers water their crops from underground water stores called aquifers, but these are drained much faster than they can be replenished. More than 300 million people in India and China rely on such non-renewable 'overpumped' water for their food. One day, that supply will run out.

Countries like China are desperate to avoid a catastrophic water crisis. In order to insure against the threat, they create dams and reservoirs, blocking up rivers so that water that falls in the wet seasons can be used in the dry.

But the rush for water security brings its own problems. When rivers flow across borders, a reservoir in one country can spell disaster in another.

Many international conflicts are already about water. India and Pakistan fight for control of the Indus. Syria and Iraq watch nervously as Turkey builds dams on the Euphrates. Endless quarrels simmer in Africa over the precious waters of the Nile.

Wars of the past were fought for oil. Wars of the future may be fought for water, which some are now calling 'blue gold.'