A Snapshot in Foreign Affairs  provides a good summary of the current state of international “hydro-politics” around the world. Here the main results:
1. In short, predictions of a Water World War are overwrought. However, tensions over water usage can still exacerbate other existing regional conflicts. Climate change is expected to intensify droughts, floods, and other extreme weather conditions that jeopardize freshwater quantity and quality and therefore act as a threat-multiplier, making shaky regions shakier.
2. By 2050 500 million people, will be at high risk for feeding into political tensions in 61 of the 276 international river basins.
3. The Nile and the Aral Sea are likely to require sustained attention, because the rights over the river have not been settled on a river-basin basis.
The short text also provides links to relevant overview studies of the subject for those who want to deepen their knowledge of the problem.
A related concept in Water Footprint, which indicates freshwater user per capita. Prof. Arjen Hoekstra in the Netherlands http://bit.ly/Pw178L is one of the world experts on Water Footprint. Her papers may be downloaded from her site. The e-institute of the World Bank provides an introduction http://bit.ly/RkvUUs .
Dinar, Shlomi, Lucia De Stefano, James Duncan, Kerstin Stahl, Kenneth M. Strzepek, and Aaron T. Wolf. "No Wars for Water." Foreign Affairs. 18 Oct. 2012. Web. 26 Oct. 2012. http://www.foreignaffairs.com/articles/138208/shlomi-dinar-lucia-de-stefano-james-duncan-kerstin-stahl-kenneth/no-wars-for-water?cid=nlc-this_week_on_foreignaffairs_co-102512-no_wars_for_water_4-102512 .