The usual process is to pump the brine back into the ocean. The amounts of fresh water we can extract are literally a drop in the ocean, and make no appreciable difference to the salinity of the seawater. That's a good idea; the easiest way to make it happen is to charge farmers the full cost of purifying and supplying the fresh water they use - if they can stay in business without making those changes once they are paying full price, then no further action is needed.
Given what I just posted the cost to farmers would go right through the roof since even while they don't pay for making water drinkable or essentially germ free they pay less than their rightful costs even good times. Their rates are about 0% of what cities pay by my quick calcs (about $2925 per acre foot in speederfundus versus about a maximum of $1000/acre ft. in the central valley (Fresno) down to $140 per acre ft prior to the drought. So speeederfundus people pay from three times to about 20 times what Fresno farmers pay.
Here's the part that important though. If we presume that water goes from about 5% to 20% of costs for producing food we can expect most food prices to jump by at least 50% even with increased foreign supply. Now speederfundus types have their grocery bills increased by about 40% or to over $400 a month for a family of three.
I believe we'd gladly pay a 25% ($5) bit more for water to get more water to the the farmers to relieve us of the added $15 a month we pay at Shittymart. So bring on the desalination micro plant.
