Nile River and the Desert

In ancient times, the Egyptians called the desert the "red land", distinguishing it from the flood plain around the Nile River, called the "black land". These colours reflect the fact that the desert sands have a reddish hue and the land around the Nile turned black when the annual flood waters receded.

The Upper Nile is divided into three tributaries (a river or stream flowing into a larger river or lake. ): the White Nile, the Blue Nile and the Atbara River. The White Nile flows from Lake Victoria, Lake Edward and Lake George, and the Blue Nile originates in the Ethiopian mountains. The Atbara River flows from the Ethiopian highlands and meets the combined White Nile and Blue Nile just north of Khartoum. Before the river enters the Mediterranean Sea, it divides into four smaller tributaries in the delta region.

The northern region of Egypt is bounded by two deserts, the mountainous Eastern, or Arabian, Desert and the sandy Western, or Libyan, Desert. Nomadic tribes continue to roam these desert regions as they have done for centuries, stopping at oases to refill their water supplies.

Around 5000 B.C., when the climate became more arid, nomadic groups retreated to the Nile Valley, creating the first urban settlements. These communities were concentrated in the North and the South. As a result, Egypt became known as the "Double Land" or the "Two Lands" of Upper and Lower Egypt.

Dualities, such as desert and river valley, Upper and Lower Egypt, life and death, were an important organizing principle of the Egyptian's world view.

https://www.historymuseum.ca/cmc/exhibitions/civil/egypt/egcgeo2e.shtml