Well, the California Coastal Commission put the kibosh a few years ago on a decades-long desalination project: https://calmatters.org/environment/2022/05/california-desali...
I haven't heard of any new desalination projects making headway since. The cost-benefit analysis may favor it, but I'm not sure the politics do. Of course, those politics will probably change in 10-15 years in our next big drought cycle, and then we'll really wish we'd gone forward with more desalination.
Doheny was approved shortly after the Huntington Beach desal plant was killed. Update from last month: https://www.ocregister.com/2025/11/26/landfill-trash-could-h...
Poseidon currently runs a desal plant in Carlsbad. My understanding is that the water the plant releases into the ocean requires exemptions for how concentrated it is. Additionally, the plant draws plankton filled water. Not really what we want in California.
There are better desal solutions out there like OceanWell. They have a deep water desalination solution that solves many of the problems of conventional desal. They just signed a project in Nice, France in the past few days. Also, they are working with the city of Las Virgines over the past few years.
If I remember correctly, the new desal plant in Doheny has a slightly different approach to draw water in from beneath the sand, using the sand as a prefilter. But I'm not sure how that works better than drawing water in from near the surface. I can't imagine how the plankton can possibly escape the suction forces drawing them into the sand.