Nice article in the New York Times yesterday by James Kanter (in the Green Column of the Global Business Section) describing how some data center site selections are valuing locations with access to water which can be used for water-side cooling.
Notably, Google's next data center in Finland is located in a former paper mill, and will use sea water for cooling. Eminently doable of course, though more expensive than using freshwater given corrosion and usually higher pumping costs. Liked the statistic that Google's five owned data centers have on average a 16% overhead for cooling (and I suppose power delivery and conditioning).
I'm not sure that I agree with the conclusion that sites with ample water supplies are less suitable for on-site generation - the assumption is that the sites will generally have climate conditions that won't favor solar PV.
First, solar PV isn't the only technology available for on-site generation, though it is particularly apt for peak load shaving. Fuel cell technology may have broader advantages by obviating some power conditioning equipment, for example.
Second, as the Google example shows, if you're using seawater for cooling, that only limits your site selection to coastal locations, and you could certainly select sites with ample PV exposure, balanced against ambient temperature conditions.
The upshot though is that leading data center operators are starting to think like industrial plant developers, carefully evaluating the inputs of their cost structures, and thinking about ways not only to drive up efficiency, but to use "natural" resources like cooling water that can lower costs.