And having done some quick math -- if we produced a high percentage of U.s. water supply from desalinization, waste salt would be hundreds of time all current salt consumption including industrial uses. If for example one quarter of our current water consumption was produced from desalinization, about 2.5 percent of the salt produced as a by-product would supply 100% of U.S. consumption. And the affect on sea life in withdrawing huge amounts of water is not trivial either. I'm not saying either the withdrawal or salt disposal are insoluable. I'm just saying that if desalinization were to supply a non-trivial fraction of our water both are real problems that would have to be dealt, and dealing with them properly would add to the cost. Desalinization costs are now down to 600-800 per acre foot. But both both uptake and salt disposal at that price tends to either be done in unsustainable ways (simply dealing inadequately with those problems) or makes use of special opportunities that simply would scale up. I suspect that *sustainable* desalinization on a large scale would cost more in $1,000 per acre foot range. Water is more precious than gold of course, but obviously this makes it the last choice -- after efficiency means have reduced consumption, and after extensive rainwater capture is instituted, since water conserving irrigation, water efficient appliances, and cisterns all save or produce water much less expensively than this.
I still think substantial desalinization will be needed. Between our current unsustainable mining of the water table, and disruption of our water supply by climate chaos, I doubt efficiency and rainwater capture alone will supply our future needs.