Like the Tigris and Euphrates rivers in Mesopotamia in modern Iraq, the Nile provided a hospitable environment for the emergence of one of the earliest and most dominant civilizations in history. The river and its annual inundations played an important role in ancient Egyptian religion and cosmology. Most of the population of Egypt since ancient times and all its cities except those near the coast 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 its banks.
In modern times, the ten nations in the Nile Basin face perhaps their greatest challenge as they confront escalating demands for water, economic opportunities, and hydroelectric power. Pressed by their growing populations and water needs and projected drops in water flow as a result of climate change, all ten Nile basin countries have joined in a 1999 accord "to achieve sustainable socio-economic development through the equitable utilization of, and benefit from, the common Nile Basin water resources."
The ability to transcend national boundaries for the benefit of the greater cause is a necessary step not only in the care and sustenance of the Nile and its peoples, but also in the preservation and stewardship of the earth's natural resources in the face of unprecedented social and environmental challenges in the twenty-first century.
The Nile and its geography
The word "Nile" comes from the Greek word Neilos, meaning river valley. In the ancient Egyptian language, the Nile is called iteru, meaning "great river," represented by the hieroglyphs shown on the right.
The Nile has two major tributaries. The Blue Nile is the source of most of the Nile's water and fertile soil, but the White Nile is the longer of the two. The White Nile rises in the Great Lakes region of central Africa, with the most distant source in southern Rwanda, and flows north from there through Tanzania, Lake Victoria, Uganda, and southern Sudan. The Blue Nile starts at Lake Tana in Ethiopia and flows into Sudan from the southeast. The two rivers meet near the Sudanese capital, Khartoum.
Both branches are on the western flanks of the Eastern Rift, the southern part of the Great Rift Valley. Another less important tributary is the Atbara, which flows only while there is rain in Ethiopia and dries quickly. The Nile is unusual in that its last tributary (the Atbara) joins it roughly halfway to the sea. From that point north, the Nile diminishes due to evaporation.
North of Cairo, the Nile splits into two branches that empty into the Mediterranean Sea: the Rosetta Branch to the west and the Damietta to the east, forming the Nile Delta.
White Nile
The source of the Nile is sometimes considered to be Lake Victoria, but the lake itself has feeder rivers of considerable size. The most distant stream emerges from Nyungwe Forest in Rwanda, via the Rukarara, Mwogo, Nyabarongo, and Kagera rivers, before flowing into Lake Victoria in Tanzania.
The Nile leaves Lake Victoria at Ripon Falls, near Jinja, Uganda, as the Victoria Nile. It flows for approximately 300 miles (500 kilometers) further, 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 ("River of the Mountain"). At the confluence of the Bahr al Jabal with the Bahr al Ghazal, itself 445 miles (720 kilometers) long, the river becomes known as the Bahr al Abyad, or the White Nile, from the whitish clay suspended in its waters. From there, the river flows to Khartoum.
The White Nile contributes approximately 31 percent of the yearly Nile discharge. During the dry season (January to June), however, the White Nile contributes between 70 and 90 percent of the total discharge from the Nile.
Blue Nile
The Blue Nile emerges from Lake Tana in the Ethiopian highlands, then flows about 850 miles (1,400 kilometers) to Khartoum, including sections that are channeled at great force through a narrow, rocky gorge. Once it joins the White Nile, they form the Nile. Some 90 percent of the water and 96 percent of the transported sediment carried by the Nileoriginates in Ethiopia, with 59 percent of the water from the Blue Nile alone (the rest being from the Tekezé, Atbarah, Sobat, and small tributaries). The erosion and transportation of silt only occurs during the Ethiopian rainy season in the summer, however, when rainfall is especially high on the Ethiopian plateau.
Cataracts and Great Bend
Two features define the Nile between Khartoum and Aswan: the cataracts and the Great Bend. Since Roman times, the cataracts kept boats from going up and down the river between Equatorial Africa and Egypt and with the massive wetlands on the upper Nile south of Khartoum have shrouded the sources of the Nile in mystery for millennia. Though six are numbered, there are actually many more. The cataracts are also significant because these define river segments where granite and other hard rocks come down to the edge of the Nile. The floodplain is narrow to nonexistent, so opportunities for agriculture are limited. For these two reasons—navigation obstacles and restricted floodplain—this part of the Nile is thinly populated. The historic border between Egypt in the north and Nubia or Sudan in the south is the First Cataract at Aswan.
The Great Bend is one of the most unexpected features of the Nile. For most of its course, the Nile flows inexorably north, but in the heart of the Sahara Desert, it turns southwest and flows away from the sea for 300 kilometers before resuming its northward journey. This deflection of the river's course is due to tectonic uplift of the Nubian Swell. This uplift is also responsible for the cataracts; if not for recent uplift, these rocky stretches would have been quickly reduced by the abrasive action of the sediment-laden Nile.
Credited to new world encyclopedia and flickr:Tewkes,Wigmspeedy
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