Also for desal, environmentally, most of the power would probably have to come from nuclear if used on a wide scale basis. And considering we are in California, nuclear could have it's own Fukushima type consequences.
I still think the best way to get water to arid regions in the nation is by pipeline from too wet regions. If you take their water say once their levels get to above 90%. it's probably enough to feed CA, TX, and the other areas under drought right now. And it would probably prevent all the flooding in areas where the water has no where to go.