Engineering solutions (RO desalination powered by photovoltaics) exist right now to deliver practically limitless amounts of potable water in a sustainable manner for around $1/m3. That is 1 cent per 10 litre bucket.
I am not sure who is feeling the pain in California... $1/m3 may be too much to pay for broadacre farming. But for city residents, who (in Australia) typically use ~300l/person/day, including lawn care, this seems very affordable.
Incidentally: Perth, Australia, used to rely on dams and groundwater to supply its needs. When I visited the dams 10 years ago they looked about what Californian dams look like now. This year, the dams are nearly full, and the annoying ads urging reduced water consumption have disappeared. What has changed? Two RO desalination plants were built, and now roughly half of Perth's fresh water supply comes from these plants. To power the plants, two small-ish wind energy farms have been built. So perhaps this is the right solution for California also...?
That figure doesn't factor in the costs of transporting the water, but these seem like minor costs to me. I wonder if there are any costs I'm not thinking of. Even if it were 3X as much, it still seems reasonable.
According to this site, Americans use ~100l/person/day.
I think we need a discussion thread for the californian drought going on. I would like to compile information in the main post and would like help compiling it. If we really are proud to be effective altruists then this is an area we should really figure out.
Any one have any good ideas on how we can help?