>What will cut back agricultural water usage (usage, not deliveries from canals) by around 2/3 in a durable way, which minimizes the hit to GDP?
Reducing agricultural subsidies would both cut back agricultural water usage and improve GDP, as most agricultural subsidies make little sense from an economic perspective, representing a net drain on productivity. They encourage farming in places not conducive to farming, leading to significant environmental degradation. Considering the strength of the agricultural lobby however such subsidies are unlikely to be repealed.
Reducing agricultural subsidies would both cut back agricultural water usage and improve GDP, as most agricultural subsidies make little sense from an economic perspective, representing a net drain on productivity. They encourage farming in places not conducive to farming, leading to significant environmental degradation. Considering the strength of the agricultural lobby however such subsidies are unlikely to be repealed.