Black Silk - Chinese J-20 Stealth Fighter Takes Off

... "We're going to see rising tensions over shared water resources, including political disputes between farmers, between farmers and cities, and between human and ecological demands for water," says Peter Gleick, a water expert and president of the Pacific Institute in Oakland, California. "And I believe more of these tensions will lead to violence"

In India: "We wake up every morning fighting over water," says Kamal Bhate, a local astrologer. In a nearby slum, a teenage boy was recently beaten to death for cutting in line.

"Peace between Pakistan and India may hinge as much on water as on Nuclear weapons for the counties must share the glacier-dependent Indus"

"The biggest question mark hangs over China, which controls the sources of the regions major rivers. It's damming of the Mekong has sparked anger downstream in Indochina. If Beijing follows through on tentative places to divert the Brahmaputra, it could provoke its rival, India, in the very region where the two countries fought a war in 1962."

Back to what you said, Desalination leaves behind a concentrated brine, which can technically harm the environment and the water supply itself. "Brine discharges are especially tricky to dispose of and they're also raising the sanity parts of the Persian Gulf. The saltier the water becomes, the more expensive it becomes to desalinate."

Desalination may be a billion dollars cheaper, but in the long term - it's not. (for now anyway). People who don't have a load of money will not be able to afford this water. What happens then?

Quotes from April 2010 National Geographic.