Desalination may seem like a magic solution to water shortages. It’s not, primarily because it’s expensive. A former mayor of Phoenix thinks the Sea of Cortez should have multiple desalination plants. Much of that water would go for irrigated farming. Watering The Desert says a far better solution is switching to low-water use irrigation. An acre foot of desal water can cost 10x more than regular water. Heavy use of desal water by agriculture also means farmers would have to switch to much higher value crops.
The part of this equation I find especially puzzling is the fact that if you are attempting to grow crops with desalinated water (even from brackish waters) the cost of the produced water is going to be significantly higher than the cost of the next likely water supply. In order to make farming work with such high input costs you need to become much more efficient in your water use and probably grow higher value crops.