The longest river in the world, flowing about 6,675 km (4,150 mi) through eastern Africa from its most remote sources in Burundi to a delta on the Mediterranean Sea in northeast Egypt. The main headstreams, the Blue Nile and the White Nile, join at Khartoum in Sudan to form the Nile proper. The river has been used for irrigation in Egypt since at least 4000 BC, a function now regulated largely by the Aswan High Dam.