There is a pressing global problem of increasing freshwater scarcity. Lack of water has led to the threat of water rationing in one of the wealthiest regions in the world, California. In one of the world's poorest countries, Yemen, a rapidly growing population and overuse of water for irrigation may mean that its capital, Sana'a, will literally run out of water in the coming decade unless there is a change in how its water is managed.

The other side to the problem is diminishing water quality, and the quality of water that is available to billions of people is dire. The Food and Agriculture Organization of the United Nations estimates that about 3800 children die every day – almost exclusively in poor countries – as a direct result of unsafe drinking water and lack of sanitation.

Without shift in how water is used and governed, scarcity and quality problems will be made much worse with the twin challenges of a growing world population and climate change; both these factors are expected to increase the frequency and severity of droughts in mid latitudes.

As per capita water volumes decrease, water conflicts will be exacerbated. In response to water scarcity, diversions of water from one area or catchment to another are likely to increase. Unfortunately, there are few places left in the world where additional water can be tapped without imposing substantial costs on existing users or on the environment.