This is a term devised by environmentalists for a type of conflict (most probably a form of guerrilla warfare) which has not yet occurred, but which they predict will happen sometime shortly after the millennium through an acute shortage of water for drinking and irrigation. About 40 per cent of the world’s populations are already affected to some degree, but population growth, climate change and rises in living standards will worsen the situation: the UN Environment Agency warns that almost 3 billion people will be severely short of water within 50 years. Experts point to the disaster of the Aral Sea, which has already lost three-quarters of its water through diversion for irrigation of the rivers feeding it. Possible flash points have been predicted in the Middle East, parts of Africa and in many of the world’s major river basins, including the Danube. The term has been used for some years, happily only in a figurative sense, to describe disputes in the southern and south-western United States over rights to water extraction from rivers and aquifers.