There are 263 cross-boundary waterways in the world. Between 1948 and 1999, cooperation over water, including the signing of treaties, far outweighed conflict over water and violent conflict in particular. Of 1,831 instances of interactions over international freshwater resources tallied over that time period (including everything from unofficial verbal exchanges to economic agreements or military action), 67% were cooperative, only 28% were conflictive, and the remaining 5% were neutral or insignificant. In those five decades, there were no formal declarations of war over water.
Three examples are explored a bit further: the Israel-Palestine, the India-Pakistan and the Nile water conflict situations. The Nile issue is about how the countries surrounding it were forced into cooperation following years of low level conflicts and the India-Pakistan issue on how cooperation has been set up in a treaty with the help of the World Bank despite the two countries being engaged in an ongoing military conflict. The Israel-Palestine issue is presented a bit weird:
it is foolish for Israel, a water-short country, to grow and then export products such as oranges and avocados, which require a lot of water to cultivate
Yes it is. Israel and most neighbours have water shortages but alleviate it by importing grain. There are a whole bunch of inconvenient truths not mentioned, but one is:
Palestinian and Israeli water professionals interact on a Joint Water Committee, established by the Oslo-II Accords in 1995. It is not an equal partnership: Israel has de facto veto power on the committee.
I'll dig out some more facts soon (in the mean time try my Israel and Palestine tags). But let's just note Wendy Barnaby's main conclusions:
Inequitable access to water resources is a result of the broader conflict and power dynamics: it does not itself cause war [...] predictions of armed conflict come from the media and from popular, non-peer-reviewed work
Undoubtedly true that main stream media is better at sensationalistic headlines than scientific journals. But is this move from simplistic causation to hen-or-egg discussion a bit too easy? I mean demand is very likely to go up, supply very likely to go down. Leading to cooperation or conflict.
water 'embedded' in traded products could be important in explaining the absence of conflict over water [...] as poor countries diversify their economies, they turn away from agriculture and create wealth from industries that use less water. As a country becomes richer, it may require more water overall to sustain its booming population, but it can afford to import food to make up the shortfall
most importantly, improve the conditions of trade for developing countries to strengthen their economies
Sure. That's what the WTO is for, right? ;-)
Barnaby, W. (2009). Do nations go to war over water? Nature, 458 (7236), 282-283 DOI: 10.1038/458282a
Search Google Books for Wendy Barnaby.