Wendy Barnaby was planning on writing a book on wars caused by water but in the course of researching the topic, she found that instances of cooperation far outnumbered any violent episodes. Between 1948 and 1999, there were no formal declarations of water over water. One explanation for the lack of bloodshed over water is attributed to "embedded" or "virtual" water - water inherent in traded goods. Barnaby explains that as a global average, a typical person is responsible for the use of 1101 cubic meters of water, for washing, cleaning, drinking, and growing food. Importing food can reduce this total significantly. Larger, wealthier countries typically depend less on domestic agriculture, focus their economy on less water-intensive industries, and can afford to import food to cover water shortages.
In the article, Barnaby focuses on various conflicts such as those between Israel and Palestinians, India and Pakistan, and Egypt, Sudan, and Ethiopia, and points out how treaties, committees, and negotiations can ameliorate water disputes. Although Barnaby admits there is conflict in those regions, conflict over water is a symptom of the larger conflict and power struggles already at play and rarely leads to violence attributed to water.
Barnaby, Wendy. (2009). Do nations go to war over water? Nature, 458, 282-283 (19 March 2009). doi:10.1038/458282a.