We can desalinate all the water we want in California — we already have a bunch of desalination facilities, and can build those out as far as need be — but desalinated water isn’t as cheap as already-fresh water. That’s mostly an annoyance for, say, residential use. But it’s harder to competitively do agriculture on desalinated water. Israel has done some limited agriculture on desalinated water, but farmers are not generally going to be okay with that as an option. Most agriculture uses a lot of water.
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Someone ran the numbers to see roughly what it would cost if we did only desalinated water for everyone in the US.
https://hannahritchie.substack.com/p/how-much-energy-does-desalinisation
Producing enough drinking water for someone — assuming 3 litres per day — costs just $2.30 for the entire year. That’s less than the cost of a single bottle of water in many countries.
We actually use way more water than we do for drinking — we’re pretty prolific with water to do things like lawns.
If the average person in the United States uses 310 litres of water per day for domestic uses, it would cost them $0.42 per day. Or $154 per year.
We’d probably want to conserve more nationally in such a scenario (Californians use less than the national average). But even with no conservation, it’s very much doable.
It’s a cost that we’d rather not pay if we don’t have to, as a society, but we certainly are able to do so for residential needs.
But if there isn’t enough freshwater to do agriculture, then who gets the freshwater determines which farmers go out of business (or at least have to shift to something else) and which get to keep operating.
There are irrigation techniques like drip line irrigation which drops water right next to the plant where it soaks in one spot instead of making a huge area on the surface damp.
You can also do subsurface irrigation but that’s more a thing for orchards or vineyards where you plant once and don’t need to plow or irrigate for a decade or two.
Desal has environmental downsides though. The biggest one is it’s an energy hog. That’s a big problem as we’re trying to decarbonize.
I do think eventually it will make sense to provide abundant desalinated water to arid, near coastal areas but there are issues with tech and infrastructure that need fixing for that to happen. Most importantly, the elimination of fossil fuels from the electric grid.
