The length of the Nile between Aswan and the Mediterranean Sea is approximately 1,200 km. Through most of Egypt, the Nile has carved a deep, wide gorge in the desert plateau, often through deposits of sediments it carried for thousands of years before construction of the Aswan High Dam. Immediately north of Aswan, the river valley is narrow with a gentle gradient and is surrounded by sandstone cliffs. These sandstone cliffs give way to limestone cliffs near Esna. Downstream 120 km from Esna, at Qena, the river bends towards the east and the river valley broadens. The Nile valley and floodplain continue to widen northward until the river reaches the delta.

At the south end of the delta, approximately 23 km north of Cairo, the Nile divides into two branches: the Rosetta branch to the west, and the Damietta branch to the east. The delta extends north for another 160 km to the Mediterranean Sea and encompasses about 230 km of Mediterranean coastline. The coastal regions of the delta contain wetlands, lagoons, lakes, and sand dunes. The delta region is densely populated and contains about 22,000 km2 of agricultural land.

The Nile valley and delta in Egypt are the result of thousands of years of annual Nile floods, in which the river overflowed its banks and deposited sediment carried from the Ethiopian highlands across the Egyptian landscape. The annual deposition of sediment replenished soil nutrients, the source of the fertility of Egypt's land. In addition, the Nile delta slowly expanded northward as sediments were deposited in the Mediterranean Sea. With the construction of the Aswan High Dam, sediments carried from the Ethiopian highlands are trapped behind the dam within Lake Nasser/Nubia. Between 1978 and 1990, more than 1.5 billion cubic metres (bcm) of sediment was deposited within Lake Nasser/Nubia. Without the annual deposition of sediments within the Egyptian Nile valley, chemical fertilizers are needed to maintain the fertility of Egypt's soils. Other changes potentially attributable to construction of the Aswan High Dam and elimination of the annual Nile flood include degradation of the delta coastline and saltwater intrusion into the delta17.





The Nile Valley in Egypt.

The waters of the Nile are heavily used for irrigation, allowing lush, green vegetation to flourish in the arid environment (Sakkara, Egypt).

Aswan High Dam hydroelectric power station.