The Nile River

Beginning of the Blue Nile River by its outlet from Lake Tana (Amhara Region, Ethiopia).

The Nile (Arabic: النيل, an-Nīl; Ancient Egyptian: Iteru & Ḥ'pī; Coptic Egyptian: ⲫⲓⲁⲣⲱ, P(h)iaro; Amharic: ዓባይ^?, ʿAbbai) is a major north-flowing river in northeastern Africa, generally regarded as the longest river in the world.^[3] It is 6,650 km (4,130 miles) long. The Nile is an "international" river as its water resources are shared by eleven countries, namely, Tanzania, Uganda, Rwanda, Burundi, Democratic Republic of the Congo, Kenya, Ethiopia, Eritrea, South Sudan, Sudan and Egypt.^[4] In particular, the Nile River provides the primary water resource and so it is the life artery for its downstream countries such as Egypt and Sudan.^[5]

The Nile has two major tributaries, the White Nile and Blue Nile. The White Nile is longer and rises in the Great Lakes region of central Africa, with the most distant source still undetermined but located in either Rwanda or Burundi. It flows north through Tanzania, Lake Victoria, Uganda and South Sudan. The Blue Nile is the source of most of the water and fertile soil. It begins at Lake Tana in Ethiopia at

12°02′09″N 037°15′53″E / 12.03583°N 37.26472°E and flows into Sudan from the southeast. The two rivers meet near the Sudanese capital of Khartoum.

The northern section of the river flows almost entirely through desert, from Sudan into Egypt, a country whose civilization has depended on the river since ancient times. Most of the population and cities of Egypt lie along those parts of the Nile valley north of Aswan, and nearly all the cultural and historical sites of Ancient Egypt are found along riverbanks. The Nile ends in a large delta that empties into the Mediterranean Sea.

Above Khartoum the Nile is also known as the White Nile, a term also used in a limited sense to describe the section between Lake No and Khartoum. At Khartoum the river is joined by the Blue Nile. The White Nile starts in equatorial East Africa, and the Blue Nile begins in Ethiopia. Both branches are on the western flanks of the East African Rift.

The drainage basin of the Nile covers 3,254,555 square kilometres (1,256,591 sq mi), about 10% of the area of Africa.^[9] The Nile basin is complex, and because of this, the discharge at any given point along the mainstem depends on many factors including weather, diversions, evaporation and evapotranspiration, and groundwater flow.

Source

The source of the Nile is sometimes considered to be Lake Victoria, but the lake has feeder rivers of considerable size. The Kagera River, which flows into Lake Victoria near the Tanzanian town of Bukoba, is the longest feeder, although sources do not agree on which is the longest tributary of the Kagera and hence the most distant source of the Nile itself.^[10] It is either the Ruvyironza, which emerges in Bururi Province, Burundi,^[11] or the Nyabarongo, which flows from Nyungwe Forest in Rwanda.^[12] The two feeder rivers meet near Rusumo Falls on the Rwanda-Tanzania border.

A recent exploration party^[13] went to a place described as the source of the Rukarara tributary,^[14] and by hacking a path up steep jungle-choked mountain slopes in the Nyungwe forest found (in the dry season) an appreciable incoming surface flow for many miles upstream, and found a new source, giving the Nile a length of 4199 miles (6758 kilometers)

Lost headwaters

Further information: List of rivers by length

Formerly Lake Tanganyika drained northwards along the African Rift Valley into the White Nile, making the Nile about 1,400 kilometres (870 mi) longer, until it was blocked in Miocene times by the bulk of the Virunga Volcanoes.

In Uganda

The Nile leaves Lake Victoria at Ripon Falls near Jinja, Uganda, as the Victoria Nile. It flows for approximately 500 kilometres (300 mi) farther, through Lake Kyoga, until it reaches Lake Albert. After leaving Lake Albert, the river is known as the Albert Nile.

In South Sudan

It then flows into South Sudan, where it is known as the Bahr al Jabal ("Sea of the Mountain", possibly from Nahr al Jabal, "River of the Mountain"). The Bahr al Ghazal, itself 716 kilometres (445 mi) long, joins the Bahr al Jabal at a small lagoon called Lake No, after which the Nile becomes known as the Bahr al Abyad, or the White Nile, from the whitish clay suspended in its waters. When the Nile floods it leaves a rich silty deposit which fertilizes the soil. The Nile no longer floods in Egypt since the completion of the Aswan Dam in 1970. An anabranch river, the Bahr el Zeraf, flows out of the Nile's Bahr al Jabal section and rejoins the White Nile.

Sudan

Below Renk the White Nile enters Sudan, it flows north to Khartoum and meets the Blue Nile.

The course of the Nile in Sudan is distinctive. It flows over six groups of cataracts, from the first at Aswan to the sixth at Sabaloka (just north of Khartoum) and then turns to flow southward before again returning to flow north. This is called the Great Bend of the Nile.

In the north of Sudan the river enters Lake Nasser (known in Sudan as Lake Nubia), the larger part of which is in Egypt.

In Egypt

Below the Aswan High Dam, at the northern limit of Lake Nasser, the Nile resumes its historic course.

North of Cairo, the Nile splits into two branches (or distributaries) that feed the Mediterranean: the Rosetta Branch to the west and the Damietta to the east, forming the Nile Delta.

Tributaries

Atbara River

Below the confluence with the Blue Nile the only major tributary is the Atbara River, roughly halfway to the sea, which originates in Ethiopia north of Lake Tana, and is around 800 kilometres (500 mi) long. The Atbara flows only while there is rain in Ethiopia and dries very rapidly. During the dry period of January to June, it typically dries up. It joins the Nile approximately 300 kilometres (200 mi) north of Khartoum.

Role in the founding of Egyptian civilization

The Greek historian Herodotus wrote that "Egypt was the gift of the Nile". An unending source of sustenance, it provided a crucial role in the development of Egyptian civilization. Silt deposits from the Nile made the surrounding land fertile because the river overflowed its banks annually. The Ancient Egyptians cultivated and traded wheat, flax, papyrus and other crops around the Nile. Wheat was a crucial crop in the famine-plagued Middle East. This trading system secured Egypt's diplomatic relationships with other countries, and contributed to economic stability. Far-reaching trade has been carried on along the Nile since ancient times.

The Ishango bone is probably an early tally stick. It has been suggested that this shows prime numbers and multiplication, but this is disputed. In the book How Mathematics Happened: The First 50,000 Years, Peter Rudman argues that the development of the concept of prime numbers could only have come about after the concept of division, which he dates to after 10,000 BC, with prime numbers probably not being understood until about 500 BC. He also writes that "no attempt has been made to explain why a tally of something should exhibit multiples of two, prime numbers between 10 and 20, and some numbers that are almost multiples of 10."^[26] It was discovered along the headwaters of the Nile (near Lake Edward, in northeastern Congo) and was carbon-dated to 20,000 BC.

Water buffalo were introduced from Asia, and Assyrians introduced camels in the 7th century BC.

These animals were killed for meat, and were domesticated and used for ploughing—or in the camels' case, carriage. Water was vital to both people and livestock. The Nile was also a convenient and efficient means of transportation for people and goods. The Nile was an important part of ancient Egyptian spiritual life. Hapy was the god of the annual floods, and both he and the pharaoh were thought to control the flooding. The Nile was considered to be a causeway from life to death and the afterlife. The east was thought of as a place of birth and growth, and the west was considered the place of death, as the god Ra, the Sun, underwent birth, death, and resurrection each day as he crossed the sky. Thus, all tombs were west of the Nile, because the Egyptians believed that in order to enter the afterlife, they had to be buried on the side that symbolized death.

As the Nile was such an important factor in Egyptian life, the ancient calendar was even based on the 3 cycles of the Nile. These seasons, each consisting of four months of thirty days each, were called Akhet, Peret, and Shemu. Akhet, which means inundation, was the time of the year when the Nile flooded, leaving several layers of fertile soil behind, aiding in agricultural growth.^[27]

Peret was the growing season, and Shemu, the last season, was the harvest season when there were no rains.^[27]

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