What do you mean by "taking from another?"  First you talk about desalinization.  I'm talking about diverting fresh water just before it enters the Pacific before it needs desalinization.  It could work wonders for California's agriculture and last I looked, the Pacific Ocean has plenty of water.

Desalinization is rapidly getting less expensive, but it's still a long way from free.  And, no, in a free country, we shouldn't "make" anyone do anything.