Although there hasn't been an actual water war fought in centuries, we see water conflicts arise all the time.
After Turkey closed off the Euphrates in the 1970's to fill a dam and show off its military might, bitter rivals Iraq and Syria banded together and threatened military intervention to reopen the Euphrates. Turkey's attempt to bolster its power and influence in the middle east was set, but the response of creating rivals to ally against them was a significant realization that water effects everyone.
Since the 1940's the planet has seen a steady increase of water related conflicts around the world. Although most end peacefully the rate at which they are occuring is alarming.