Nile

The Nile is a major north-flowing river in northeast Africa which empties into the Mediterranean Sea. At 7,088 kilometres (4,404 mi) long, it is the longest river in the world, although the volume of water it carries is much smaller than other major rivers such as the Amazon or the Congo. The Nile has played a central role in the environmental, economic, and cultural history of Africa for millennia.

The Nile has two major tributaries: the White Nile and the Blue Nile. The White Nile is longer and is considered to be the headwaters, although the Blue Nile contributes over two thirds of the water and silt below the confluence of the two. The White Nile begins near Lake Victoria and flows through Uganda and South Sudan, while the Blue Nile begins near Lake Tana in Ethiopia and flows into Sudan from the southeast. The two rivers meet at the Sudanese capital of Khartoum. From there, the Nile flows north through the Nubian Desert to Egypt's capital, Cairo, and finally empties into the Mediterranean Sea near Alexandria, where it has formed a large delta.

Geologically, the Nile is a young river and has followed its present course for about 12,000 years. Its drainage basin extends across portions of eleven countries. Most of the water in the Nile comes from rainfall in the upstream countries Ethiopia, Kenya, Tanzania, and Uganda. Downstream countries – Egypt, Sudan, and South Sudan – are primarily desert, and withdraw river water for irrigation. Other countries in the Nile Basin are Burundi, Democratic Republic of the Congo, Eritrea, and Rwanda.

The Nile was the foundation of the Ancient Egyptian civilization, which relied on the river for nearly every aspect of life. The annual flooding of the river deposited nutrient-rich silt along the riverbanks. This soil supported crops that enabled a sophisticated society to thrive in an otherwise inhospitable desert. The Nile facilitated trade, communication, transportation, and governance. In the Ancient Egyptian religion, the river was personified by the Egyptian gods Hapy and Khnum. The source of the Nile was not definitively identified until the late 19th century, when Europeans explored the region around Lake Victoria.

In the modern era, the Nile plays a critical role in the economy of countries in the Nile basin, particularly Egypt and Sudan, which rely on it to irrigate extensive croplands. Since the late 20th century, over a dozen dams have been built in the Nile Basin to provide for irrigation and to generate electricity. The dams have altered the river's annual flood cycle and restricted the transport of silt downstream, causing the Nile Delta to shrink. Some dams – such as the Aswan High Dam and Grand Ethiopian Renaissance Dam – have been the source of international political disputes about water scarcity, safety, food security, and forced displacement of peoples.