[logfromblammo]

You don't need to boil water to create an artificial cloud. Or at least you don't need to heat it to vapor pressure of one whole atmosphere.

The freshwater sources wouldn't necessarily need to deal with the phase change energy, but the saltwater sources would have to be desalinated. It would still be a huge, huge amount of energy. And it would have to be added to the water multiple times, for each time it rains out before crossing the mountains.

Much easier to just build the cities closer to where the water falls naturally.