My question is actually two questions in one. I believe that in my studies in school I learned that a water column is a stand of water in a pipe to a certain height. If the pipe ended at the bottom of a tank then the water column would extend up through the water in the tank to the water level but the column would still only be the diameter of the pipe below the tank. In other words if a two inch diameter pipe took the water up to the tank the water column would be two inches of water reaching all the way to the top of the water level in the tank.

The second part of the question is would it take more power to push the water up to fill the tank be greater or less than if you used the same size pipe and ran the pipe along the outside of the tank to the top of the tank, and then over into the tank. The height of the tank would be taller that the water level in the tank itself.