[refurb]

it overlooks a significant externality: the destruction of the environment as rivers are pumped dry and (albeit, artificial) reservoirs run dry

Not sure I understand. The rivers would run dry because of no rain, not because we're taking water from them. Remember all this water we're using for irrigation was just ending up in the ocean anyways.

[DougWebb]

Is the California produce you buy bone-dry? Probably not. It's full of that precious water. A lot may wind up in the ocean as runoff, but a lot gets exported from CA too. It eventually winds up back in the ecosystem, but the point is that it will take eons to get back into the acquifers.