David Henderson explains:
Of the 80 million acre feet a year of water use in California, only 2.8 million acre feet are used for toilets, showers, faucets, etc. That’s only 3.5 percent of all water used.
One crop, alfalfa, by contrast, uses 5.3 million acre feet. Assuming a linear relationship between the amount of water used to grow alfalfa and the amount of alfalfa grown, if we cut the amount of alfalfa by only 10 percent, that would free up 0.53 million acre feet of water, which means we wouldn’t need to cut our use by the approximately 20 percent that Jerry Brown wants us to.
What is the market value of the alfalfa crop? Alexander quotes a study putting it at $860 million per year. So, assuming, for simplicity, a horizontal demand curve for alfalfa, a cut of 10% would reduce alfalfa revenue by $86 million. (With a more-realistic downward-sloping demand for alfalfa, alfalfa farmers would lose less revenue but consumers would pay more.) With a California population of about 38 million, each person could pay $2.26 to alfalfa growers not to grow that 10%. Given that the alfalfa growers use other resources besides water, they would be much better off taking the payment.
