I have a lot of fun pondering the effects of a longer term drought. Will populations shift north to Oregon and Washington? Will desalination technologies advance to significantly reduce the cost?
They have a huge desalination plant coming online soon in San Diego.[1] There are about 15 others that are proposed. With California's vast coastline and huge concentration of population along the coast, it seems logical to build more of these plants. However, they do use a lot of energy (which could be supplied by solar and wave power) and may have deleterious effects on sea life in the vicinity of the salty output. But what choices do they have, really? Until people move northward or eastward, as you suggest, or other ways to conserve are implemented, they're in a very tight spot right now. I think desal is the best option.
New desalination technologies may also provide the key, such as the RO/PRO so-called "reverse osmosis" approach[2]. The Israelis have a giant plant "Sorek"[3] that is purifying seawater on a large scale and using advanced technology to reduce the energy cost and improve efficiency. So there's some hope for this approach to providing purified water on a large scale.
