Wendy Barnaby dispels the myth of future water wars, arguing that countries “solve their water shortages through trade and international agreements” (see Nature 458, 282–283; 2009). But water has often been the object, target or weapon of military or terrorist action, including in former conflicts between Iraq and Iran, Syria and Iraq, Israel and Syria, and South Africa and Lesotho (see Peter H. Gleick's water conflict chronology at http://tinyurl.com/ce776f). These range from small-scale demonstrations and border skirmishes to the destruction of irrigation and water-supply systems and the poisoning of water supplies.
Problems can arise when humans have too little or too much water, or water that is too dirty, and countries may accuse one another of amplifying these problems. But if a pollution incident in one country kills biological life in an international river, the downstream riparian nations will collaborate to reduce damage and prevent reoccurrence; likewise, countries usually cooperate after a disastrous flood. More difficult conflicts can arise in areas of water scarcity, but nations are increasingly willing to negotiate rather than to go to war.
A handful of arid-climate countries receive nearly all their water from abroad by means of shared rivers. The water resources of Turkmenistan, Egypt, Uzbekistan, Syria and Israel depend on neighbouring countries. Several countries successfully share international rivers within the framework of river commissions, as well as lakes and aquifers through international bodies. Small-scale water disputes can lead to the development of diplomacy and help to prevent bigger water wars.
However, the potential for water conflict is on the increase, as populations in water-stressed areas continue to grow and the demand for water increases to improve living standards with better sanitation and a water-intensive diet. In arid areas, water scarcity is likely to be exacerbated by climate change (B. Bates et al. Climate Change and Water Intergovernmental Panel on Climate Change; 2008; http://tinyurl.com/c4kd2e). The potential for water conflict — war or no war — deserves careful attention.