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The Nile River

The Nile is usually considered the longest river in the world, but whether the Nile is actually longer than South America's Amazon still remains the subject of much debate. This is, for the most part, due to two reasons: first, the lengths of rivers vary over time (especially in plains, where rivers often change course), and, second, the point from which the length of a river is measured is not always agreed upon.

If the remote headstream — the Ruvyironza — is taken as the beginning and followed to the Mediterranean, the Nile is approximately 6695 km (4160 miles) long. Measuring instead from Lake Victoria gives a length of approximately 5584 km (3470 miles). It drains approximately 2.8 million to 3.4 million km² (1.1 million to 1.3 million mile²).
There are two great branches of the Nile: the White Nile, from equatorial East Africa, and the Blue Nile, from Ethiopia. Both branches formed on the western flanks of the East African Rift, which is the southern African part of the Great Rift Valley.

Lake Victoria in Uganda is commonly considered to be the source of the Nile, although the lake itself has feeder rivers of considerable size from the other Great Lakes of Africa. In particular, the farthest headstream of the Nile is the Ruvyironza River in Burundi, which is an upper branch of the Kagera River. The Kagera flows for 690 km (429 miles) before reaching Lake Victoria.

Leaving Lake Victoria, the river is known as the Victoria Nile. It flows further for approximately 500 km (300 miles), through Lake Kyoga, until it reaches Lake Albert. After leaving Lake Albert, the river is known as the Albert Nile. It then flows into Sudan, where it becomes known as the Bahr al Jabal. At the confluence of the Bahr al Jabal with the Bahr el Ghazal, itself 720 km (445 miles) long, the river beomes known as the Bahr al Abyad, or the White Nile, from the clay suspended in its waters. From there, the river flows to Khartoum.

Meanwhile, the Blue Nile (or Bahr al Azraq to Sudanese; Abbai to Ethiopians) springs from Lake Tana in the Ethiopian Highlands. The Blue Nile flows about 1,400 km (850 miles) to Khartoum, where the Blue Nile and White Nile join to form "the Nile." Most of the water carried by the Nile originates from Ethiopia, but this runoff only happens in summer, when the great rains fall on the Ethiopian Plateau; the rest of the year the great rivers draining Ethiopia to the Nle (Sobat, Blue Nile, and Atbara) flow weakly or are dry.

After the Blue and White Niles merge, the only remaining major tributary is the Atbara River, which originates in Ethiopia north of Lake Tana, and is approximately 800 km (500 miles) long. It joins the Nile approximately 300 km (200 miles) past Khartoum. The Nile is also unusual in that its last tributary (the Atbara) joins it approximately halfway to the sea. From that point north, the Nile diminishes because of evaporation.

The Nile in Sudan is distincitve for two reasons: 1) it flows over 6 groups of caaracts, from the first at Aswan to the sixth at Sabaloka (just north of Khartoum); and 2) it reverses course for much of its course, flowing back to the SW before returning toflow north again tothe sea. This is the "Great Bend of the Nile".

The Great Bend of the Nile in Sudan, looking north across the Sahara Desert towards Lake Nasser and Egypt. Photograph ISS006-E-43181 taken from the International Space Station, courtesy of NASA.The Nile then reaches the man-made Lake Nasser, impounded behind the Aswan High Dam 270 km (170 miles) into Egypt from the Sudanese border. Since 1998 some of Lake Nasser's waters have spilt westward to form the Toshka Lakes. From Lake Nasser the main channel flows north through Egypt and into the Mediterranean Sea; a side channel, the Bahr Yussef, splits from the main channel downriver from the city of Asyut, and empties into the Fayum. Where the Nile meets the Mediterranean, the Nile Delta, is the eponym of all river deltas worldwide. Enrichment from Nile sediments carried eastward by currents nurture the fishing industries of the Eastern Mediterranean, or used to before the Aswan High Dam was built.

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Nile".