Herodotus said "Egypt is the gift of the Nile "and he was correct.
There is no doubt without the Nile river and its unique annual inundation the ancient Egyptian civilization would have suffered the same fate as the Mesopotamians and Sumerians and it most certainly would not have developed into the magnificent culture it did.
Each year in June the tropical rains that fall in the ancient volcanic ranges of Ethiopia and Uganda would reach Egypt and the Nile river would flood the ribbon of flat lands along its bank.
When the flooding subsided the water left behind a layer of nutrient rich black loam.This soil was so important to the Egyptians agrarian culture that they referred to themselves as kmt or kemet "the people of the black land ".
The Nile not only provided a continual source of fresh water it was also the super highway of the ancient Egyptians.
It was via the Nile the huge granite blocks used in the construction of the pyramids and other important monuments and building were brought from Aswan in Upper Egypt to Giza and Saqqarra and other locations.
It is only since the construction of the Aswan Dam,which controls the amount of water that flows into Egypt and ended the cycle of the inundation, that Egyptian farmers have found it necessary to use fertiliser to ensure the growth of the crops.
This is a very good essay on the Nile river and its role in Egypt's development.
http://www.touregypt.net/featurestories/nile.htm