Kevin Williamson has an excellent article in the National Review on how California is (and how it should be) dealing with it's drought-induced water shortage.
He frames the problem as one that should be familiar to any economist: how do we allocate a scarce resource. He also makes the point that scarcity is a fact of reality that cannot be wished away or swept under the rug.
About agriculture, he writes:
So, how should we allocate water?
More precisely, here's a route forward.
To the extent one is worried about the poor being able to afford water, use block rate pricing or take some of the receipts from the sale of water and re-allocate to the poor to let them decide whether it is worth buying.