And /energy/. A /lot/ of energy.
There are already movements of raw water between regions. More are planned in companies' strategic plans. But when you've used up the easy options ("downhill all the way!") it involves pumping. That's energy intensive 'cos water is heavy. It's also not worth a lot per per tonne. So it's hard to get the sums to add up unless the price goes up a lot or (as with so many engineering problems) energy becomes cheaper.