Desalination of seawater is the ultimate solution. But some enviro extremists oppose desalination because desalinating n plants produce waste, such as salt and other minerals found in seawater. Also, desalination plants run from fossil fuels.
There is currently a desalination plant under construction in southern California. But given the enviro extreme opposition I doubt there will be more such projects allowed.
For drinking water, maybe. But, it will never be a solution for irrigation, unless there is a widespread switch to more efficient irrigation methods that don't lose most of it to evaporation.
It requires about 10 Kilowatt hours to desalinate 1,000 gallons of water on an industrial scale, using reverse osmosis. You can do the math and figure out how that won't work for irrigation.