The linked article from The New Yorker entitled: "A Thirsty, Violent World", concludes (see extract) that coming water wars are rooted in our inherent aggressive nature:
http://www.newyorker.com/news/daily-comment/coming-water-warsExtract: "The result of continued inaction is clear. Development experts, who rarely agree on much, all agree that water wars are on the horizon. That would be nothing new for humanity. After all, the word “rivals” has its roots in battles over water—coming from the Latin, rivalis, for “one taking from the same stream as another.” It would be nice to think that, with our complete knowledge of the physical world, we have moved beyond the limitations our ancestors faced two thousand years ago. But the truth is otherwise; rivals we remain, and the evidence suggests that, until we start dying of thirst, we will stay that way."