Two words: water desalination. Texas and Cali have a very good water future. Its states like Colorado where the water wars are going to be continuing for a long, long time.
Going by the estimates in the original post, Texas will have have a water deficit of 6.3 million acre feet per year by 2060; converting to more sensible measurements, that's a deficit of just over 5.6 billion gallons per day.
Now, consider that world's biggest desalination plant, in the UAE, has a maximum output of 130 million gallons per day. So for Texas to make up its water deficit with desalination plants, it would need to build 43 of them equivalent in output to the most productive one in the world. I think this probably counts under "huge infrastructure project getting under way yesterday," and I don't really think it'd be all that cheap either.
