Northern Italy is pretty wet due to the rain / snow inducing effect of the Alps. It makes no economic sense to build multi billion dollar desal plants that are not needed until a 70 year occurrence drought.
What the world actually needs is nuclear power plants on barges with huge desal units on their turbine exhaust heat. This way you can build out a few of those and then tow them to where they might be needed for only a few months or a year then move on. This spreads the capital costs over a whole area and also allows for the Henry Ford method of manufacturing build them in a shipyard assembly line style using one certified design again and again if you need more power add more modules of the same reactor design. A 200mw aircraft carrier sized PWR would be in the 30000 ton class three of them would fit on a 90,000 ton barge that would still fit in the Panama Canal.