Most years it drops on South Asia in a seasonal monsoon. A huge proportion drains from great rivers that run through largely unoccupied countryside, such as the Ob and the Yenisei in Siberia, or the Amazon in Brazil. How precious was demonstrated by a team from Stanford University, California, in 1996. It might, she argues, be difficult to use much more. Most land suitable for rain-fed agriculture is already being used.
Water is life's bottom line.
Humans are just bags of water. A man weighing 70kg will contain 43 litres of water, and even in a mild climate he will lose 2.5 litres a day by respiration, perspiration and urination. Water is also, in effect, food. Every eight seconds a child dies of a water-borne disease. Paradoxically a clean water supply is the most powerful single force in public health.