Of course this goes for new desalination plants. Whether there's political will to convert existing plants to non-fossil fuel sources is another matter. But at least from an engineering perspective there is a way forward.
What I get out of the article is that disposing of brine is an ecological hazard. This shouldn't really be a surprise since any engineering effort at large scale is going to have some kind of environmental impact, but this is a new consideration for those of us who don't work in the industry and hadn't thought too deeply about the process.
To be able to "build up reserves" means that you have to build much higher capacity, but only use as much of it as clean energy allows - in today's world, this is highly uneconomical.
If anything, the reserves to be built are energy reserves that allow water to be desalinated continuously -- and that's something which makes sense in general, possibly grid scale as storage technology improves, regardless of the specifics of water desalination.
I believe this is coming about because: 1) the high cost of power and presence of sporadically cheap power makes it economically viable, and 2) designing equipment with lower duty cycles can actually provide substantial cost savings. Ie a facility which only runs 50% of the time is much cheaper to build & run than once which runs 100% of the time.
Sorry I cannot cite sources right now.
To take truly economically fantastic extremes for current technology if desalination was fiscally cheaper than drilling wells we would see them doing that far more.
[0] https://www.watercorporation.com.au/water-supply/our-water-s...
Sound like really obvious places to use solar.
Desalination is good for drinking water but its not going to save California's farming though.