The point isn't that the area can't supply its own water, nor that upstate NY can't supply enough water for NYC. The point is that even in a water-rich region, a city like NYC (or even one the size of Albany) cannot support its population off well water. Thus the existence of modern economic centers is dependent on piping in water. Telling city dwellers that they should get their water from wells so as to avoid dependence on their neighbors for their water is an absurdity.