That could actually get farmers to increase alfalfa production. Alfalfa water usage per acre is not much different than that of spinach, tomato, lettuce, wheat

That could actually get farmers to increase alfalfa production. Alfalfa water usage per acre is not much different than that of spinach, tomato, lettuce, wheat, or corn. As an aggregate it uses more water because (1) there is a lot of acreage of alfalfa, and (2) it can be grown nearly year around. Furthermore, its water efficiency (how much is produced per unit of water used) is high. If water costs go up some farmers might be able to make more money then by switching to alfalfa since it is more efficient.