The Nile is the longest river in Africa. It flows generally northwards through Uganda, Sudan and Egypt. The main tributary, the White Nile, springs from Lake Victoria in Uganda. It then flows into Lake Kyoga before heading through Sudan. Near Khartoum it is joined by the Blue Nile, the second major tributary, which springs from Lake Tana in the Ethiopian Highlands. In Egypt it then flows into the Mediterranean Sea at Alexandria.
The Nile was the lifeline of the ancient Egyptian civilization, with most of the population and all of the cities of Egypt in the Nile valley. It still supports much of the population of Egypt, living between otherwise inhospitable regions of the Sahara Desert. The river flooded every spring, depositing fertile soil on the fields. The flow of the river is disturbed at several points by cataracts, which are sections of faster flowing water with many small islands, shallow water and rocks, forming an obstacle to navigation by boats. The first cataract, the closest to the mouth of the river, is at Aswan to the north of the Aswan Dams.
The Nile north of Aswan is a regular tourist route, with cruise boats and falukas, which are traditional wooden sailing boats.
While most Egyptians still live in the Nile valley, the construction of the Aswan High Dam to provide hydroelectricity ended the spring floods and their renewal of the fertile soil.