[manholio]

Desalination is exceptionally expensive compared to just waiting to have water fall from the sky.

You can do it in extremely arid climates, for example to provide water to cities, but it makes no economic sense when you already have huge amounts of free water that you waste on inefficient irrigation techniques.

[baragiola]

California is extremely rich. You have a water shortage. Water is important

[manholio]

Those three premises are still insuficient to warant desalination.

"Shortage" means little, what we have is a restricted supply curve, that can still meet demand at a higher price. And if that price is insuficient to pay for desalination then it won't happen: when you build your desalination plant and try to sell water at production costs, you won't find any takers. They'll tell you yes, we have a shortage, water prices have exploded by 100%, 2 cents instead of 1 cent, but they certainly won't pay you 10c for desalination.