Why is upper Egypt in lower past?

The Nile begins from the center of Africa going out of lake Vittoria with the Ripon falls, at a height of 133 m above the sea level. Then it begins its long course toward North, that is toward the valley, toward the Mediterranean, so toward level “zero” on the sea level. It’s obvious that the river, flows from a higher level to a lower one; to this refers the definitions of upper (the valley, upstream) and lower (the delta) Egypt. Besides in ancient Egyptian cartography the north was in the low part.