Cape Town Africa ?
I was once a plant operator for a company that pumped water into an underground soda formation. Then brought the brine up and boiled it, which separated the soda from the water. The water came out pretty clean. The article above talks about desalination plants being held up in bureaucracy. I have never understood why any large city by the ocean would not be using this technology. They can use solar concentrators to heat the water and power the plant.
Other than that it seems that there are just to many folks in that drainage wasting too much water.
Never been there but looking at a Google map tells a lot of the story? Massive amounts of farm land under conventional modern farm management. Lots of plowing, dry land left fallow, etc. Do the irrigate all of that?