The river carves a narrow, cultivated floodplain, never more than 20 kilometers wide, as it travels northward toward Cairo from Lake Nasser on the Sudanese border, behind the Aswan High Dam. Just north of Cairo, the Nile spreads out over what was once a broad estuary that has been filled by riverine deposits to form a fertile delta about 250 kilometers wide (150 mi.) at the seaward base and about 160 kilometers (96 mi.) from south to north.

Before the construction of dams on the Nile, particularly the Aswan High Dam (started in 1952, completed in 1970), the fertility of the Nile Valley was sustained by the water flow and the silt deposited by the annual flood. Sediment is now obstructed by the Aswan High Dam and retained in Lake Nasser. The interruption of yearly, natural fertilization and the increasing salinity of the soil has been a manageable problem resulting from the dam. The benefits remain impressive: more intensive farming on millions of acres of land made possible by improved irrigation, prevention of flood damage, and the generation of billions of low-cost kilowatt hours of electricity.

The Western Desert accounts for about two-thirds of the country's land area. For the most part, it is a massive sandy plateau marked by seven major depressions. One of these, Fayoum, was connected about 3,600 years ago to the Nile by canals. Today, it is an important irrigated agricultural area.