Water, like any scarce common resource, creates competition that can lead to conflict, but, as Wendy Barnaby concludes in her Essay, wars are not waged over water (see Nature 458, 282–283; 2009). Her message is borne out by my own experience as senior adviser to the Israeli Water Authority.
The Jordan-Israel Peace Treaty, signed in October 1994, includes a chapter on water that has been in operation for more than 14 years to the satisfaction of both parties. Jordan's chief water negotiator, Munther J. Haddadin, in a review of the history that led up to the treaty, notes that “The claim that the June war of 1967 was a 'water war' is not substantiated” (M. J. Haddadin Diplomacy on the Jordan Kluwer; 2001).
In 1995 Israel signed the Oslo II Interim Agreement with the Palestinian Authority, in which Article 40 ('Water and sewage') was intended to serve for a period of five years while a permanent agreement was drawn up. Although this has not yet happened, both sides adhere to the interim agreement as a basis for coordinated management of their water resources. Despite the difficult security situation, the Joint Water Committee set up by the agreement has met and communicated regularly, and Israel has increased the water supply to the Palestinian Water Authority over and above that stipulated in the agreement, in response to Palestinian needs and requests.
Water, by its very nature, has a proven potential for engendering cooperation between nations rather than being a cause for war.