Pretty sure it runs horizontally. Vertical channel would be called waterfall.
But we both knew that.
Yes, we tried showing her the Nile.
Also:
What if north is facing down?
What if map is not on a wall but on a table?
What if map is not oriented not in north-south direction?
https://en.wikipedia.org/wiki/Falkirk_Wheel
Pretty sure it runs horizontally. Vertical channel would be called waterfall.