MIT's Technology Review has an article on San Diego's current state of the art desalination plant.
Desalination out of Desperation
Severe droughts are forcing researchers to rethink how technology can increase the supply of fresh water.
By David Talbot on December 16, 2014
One of the graphics shown is the amount of power used to produce a cubic meter (264 gals) of water.
What the article doesn't mention is the amount of water consumed to generate power in San Diego. The DOE has a paper you can check out on water use in thermoelectric power generation. 67% of SD power comes for natural gas plants. 24% renewable
Here is a graphic to show the areas of water use in thermoelectric power plant.
For an example of thinking about water use in the data center check out this Google video on the use of gray water.