California has already invested a lot into reservoirs. In fact, as a pilot, I recall noticing that nearly all lakes in California are actually man-made reservoirs. I doubt there is much room left for economically building more; all the easy ones have been taken, and more. Surely the cost benefit of just investing a lot into desalination must be getting close.

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.

Desalination must be insanely expensive; I’m always shocked it wasn’t done decades ago.

Considering California always seems to have power and water issues, I’d think combining these things would make a lot of sense. Some of these exist and there seems to be a fair bit of research in the area. I have to image at some point that will be the direction California would need to go. Of course, if they are all-in on solar and wind, then maybe not.

> nearly all lakes in California are actually man-made reservoirs

This is sometimes true even in much wetter states, though. I recall being thoroughly surprised to find that out that Virginia (!) has only two natural lakes, one of which is basically just an open area (though a large one) of the Great Dismal Swamp.