[tzs]

How is alfalfa being exported relevant? Only 0.005% of the water used to grow alfalfa ends up in the alfalfa itself. Almost all of the water used for growing alfalfa ends up in the local atmosphere via either evaporation from the soil or transpiration from the plants.

Before one can reasonably discuss the impact of alfalfa growing one needs to figure out what happens to that 99.995% of the water that ends up initially in the local atmosphere. What places does it end up? How long does it take to get there? How much of this process is a loop?

I've not been able to find answers to those questions.

[scruple]

Most of the alfalfa grown in California is in the San Joaquin Valley. Overdrafting is a well understood phenomenon at this point. No, there is not an efficient loop to be found here without significant investment in recharge infrastructure that we currently do not have.