Water is the source of life and the building block of all civilisation. The control of water has shaped politics, health, population growth, city planning, technology and religion. Controlling water has driven progress, through the growth of intensive farming and industrial revolution. It has also become a symbol of our civilisation - evidence that we have mastered nature.From the hanging gardens of Babylon and the ancient myth of the Nile to the fountains in Las Vegas, water is the one constant. We are fed by irrigated fields, live in plumbed cities, and turn on a tap without a moment's thought. Yet, this simple technology that underpins everything is at bursting point. There are too many people for the available water, and war may follow. How did we get here, and what can we do about it?