The Nile River basin, which covers about one-tenth of the area of the continent, served as the stage
for the evolution and decay of advanced civilizations in the ancient world. On the banks of the river
dwelled people who were among the first to cultivate the arts of agriculture and to use the plow. The
basin is bordered on the north by the Mediterranean; on the east by the Red Sea Hills and the
Ethiopian Plateau; on the south by the East African Highlands, which include Lake Victoria, a Nile
source; and on the west by the less well-defined watershed between the Nile, Chad, and Congo
basins, extending northwest to include the Marrah Mountains of Sudan, the Al-Jilf al-Kabīr Plateau of
Egypt, and the Libyan Desert (part of the Sahara).
The availability of water from the Nile throughout the year, combined with the area’s high
temperatures, makes possible intensive cultivation along its banks. Even in some of the regions in
which the average rainfall is sufficient for cultivation, marked annual variations in precipitation often
make cultivation without irrigation risky.