Solutions

Rivers are too valuable to be squandered and squabbled over in this way. The few rivers that remain largely uncontrolled by dams and abstractions are sources of huge natural wealth. The magnificent fisheries of the Mekong in Cambodia allow one of the poorest countries in the world to be among the best fed.

There is so much waste of water across the world that there is also huge potential to manage things better. Villages in India and China are reviving ancient methods of capturing the rain as it falls and pouring it down their wells. Indian farmers are using perforated bicycle inner tubes as a cheap method of irrigating their crops from meagre water supplies. Some communities in Syria still rely on thousand-year-old tunnels, known as qanats, that deliver underground water by gravity.

All these systems can show us more sensible ways to manage the world's scarce water reserves - ways that involve less concrete, fewer big pipes and fewer disputes. For when the rivers start to run dry we are all in trouble.