Nile River, Arabic Baḥr Al-Nīl or Nahr Al-Nīl, the longest river in the world, called the father of African rivers. It rises south of the Equator and flows northward through northeastern Africa to drain into the Mediterranean Sea. It has a length of about 4,132 miles (6,650 kilometres) and drains an area estimated at 1,293,000 square miles (3,349,000 square kilometres). Its basin drains into Lake Victoria includes parts of (Tanzania, Kenya, Uganda). The Nile River was critical to the development of ancient Egypt. In addition to Egypt, the Nile runs through or along the border of 10 other African countries, namely, Burundi, Tanzania, Rwanda, the Democratic Republic of the Congo, Kenya, Uganda, Sudan, Ethiopia, and South Sudan. Its three main tributaries are the White Nile, the Blue Nile, and the Atbara. And the cultivated part of Egypt. Its most distant source is the Kagera River in Burundi.
The Nile is formed by three principal streams: the Blue Nile, and the Atbara which flow from the highlands of Ethiopia, and the White Nile, the headstreams of which flow into Lakes Victoria and Albert.
The name Nile is derived from the Greek Neilos (Latin: Nilus), which probably originated from the Semitic root naḥal, meaning a valley or a river valley and hence, by an extension of the meaning, a river. The fact that the Nile—unlike other great rivers known to them—flowed from the south northward and was in flood at the warmest time of the year was an unsolved mystery to the ancient Egyptians and Greeks. The ancient Egyptians called the river Ar or Aur (Coptic: Iaro), “Black,” in allusion to the colour of the sediments carried by the river when it is in flood. Nile mud is black enough to have given the land itself its oldest name, Kem or Kemi, which also means “black” and signifies darkness. In the Odyssey, the epic poem written by the Greek poet Homer (7th century BCE), Aigyptos is the name of the Nile (masculine) as well as the country of Egypt (feminine) through which it flows. The Nile in Egypt and Sudan is now called Al-NÄ«l, Al-Baḥr, and Baḥr Al-NÄ«l or Nahr Al-NÄ«l.
For thousands of years, the river has provided a source of irrigation to transform the dry area around it into lush agricultural land. Today, the river continues to serve as a source of irrigation, as well as an important transportation and trade route.
The Nile River has been a central feature of life in northeast Africa for thousands of years. Even today, families come to gather water from the riverbank, surrounded by ruins left by ancient civilizations.
The soil of the Nile River delta between El Qâhira (Cairo) and the Mediterranean Sea is rich in nutrients, due to the large silt deposits the Nile leaves behind as it flows into the sea. The banks of the Nile all along its vast length contain rich soil as well, thanks to annual flooding that deposits silt. From space, the contrast between the Nile's lush green river banks and the barren desert through which it flows is obvious.
For millennia, much of Egypt's food has been cultivated in the Nile delta region. Ancient Egyptians developed irrigation methods to increase the amount of land they could use for crops and support a thriving population. Beans, cotton, wheat, and flax were important and abundant crops that could be easily stored and traded.
The Nile River delta was also an ideal growing location for the papyrus plant. Ancient Egyptians used the papyrus plant in many ways, such as making cloth, boxes, and rope, but by far its most important use was in making paper. Besides using the river's natural resources for themselves and trading them with others, early Egyptians also used the river for bathing, drinking, recreation, and transportation.
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.
This basin receives drainage from numerous other streams. The Al-Ghazal (Gazelle) River flows in from western South Sudan, joining the Al-Jabal at Lake No, a large lagoon where the main stream takes an easterly direction. The waters of the Al-Ghazal undergo extensive loss through evaporation, and only a small proportion of them ever reach the Nile. A short distance above Malakal the main stream is joined by the Sobat (Baro in Ethiopia), and downstream from there the river is called the White Nile. The regime of the Sobat is quite different from the steady flowing Al-Jabal, with a maximum flow occurring between July and December; the annual flow of the Sobat is about equal to the water lost through evaporation in Al-Sudd marshes.
The White Nile, about 500 miles in length, supplies some 15 percent of the total volume entering Lake Nasser (called Lake Nubia in Sudan) downstream. It begins at Malakal and joins the Blue Nile at Khartoum, receiving no tributaries of importance. Throughout this stretch the White Nile is a wide placid stream, often having a narrow fringe of swamps. The valley is wide and shallow, thus causing a considerable loss of water by both evaporation and seepage.
The Blue Nile drains from the lofty Ethiopian Plateau, where it descends in a north–northwesterly direction from a height of about 6,000 feet above sea level. Its reputed source is a spring, considered holy by the Ethiopian Orthodox Church, from which a small stream, the Abay, flows down to Lake Tana (T’ana), a fairly shallow lake with an area of about 1,400 square miles. The Abay leaves Lake Tana in a southeasterly direction, flowing through a series of rapids and plunging through a deep gorge. It is estimated that the lake supplies the river with only about 7 percent of its total flow, but this water is important since it is silt-free. The river then flows west and northwest through Sudan to join the White Nile at Khartoum. In the greater part of its course from Lake Tana down to the Sudanese plains, it runs in a canyon that in places is 4,000 feet below the general level of the plateau. All of its tributaries also run in deep ravines. While the White Nile at Khartoum is a river of almost constant volume, the Blue Nile has a pronounced flood season (late July to October) caused by the summer monsoon rains over the Ethiopian Plateau and the rapid runoff from its numerous tributaries; historically, it was this surge that contributed most to the annual Nile floods in Egypt.
How the Nile was measured?
A Nilometer was a structure for measuring the Nile River's clarity and water level during the annual flood season.There were three main types of Nilometers, calibrated in Egyptian cubits: (1) a vertical column, (2) a corridor stairway of steps leading down to the Nile, or (3) a deep well with culvert. If the water level was low, there would be less food. If it was too high, it would be destructive. There was a specific mark that indicated how high the flood should be if the fields were to get good soil.
Between July and November, the reaches of the Nile running through Egypt would burst their banks and cover the adjacent flood plain. When the waters receded, around September or October, they left behind a rich alluvial deposit of exceptionally fertile black silt over the croplands. The akhet, or Season of the Inundation, was one of the three seasons into which the ancient Egyptians divided their year.
The annual flood was of great importance to Egyptian civilization. A moderate inundation was a vital part of the agricultural cycle; however, a lighter inundation than normal would cause famine, and too much flood water would be equally disastrous, washing away much of the infrastructure built on the flood plain. Records from AD 622–999 indicate that, on average, 28% of the years saw an inundation that fell short of expectations.
The ability to predict the volume of the coming inundation was part of the mystique of the Ancient Egyptian priesthood. The same skill also played a political and administrative role, since the quality of the year's flood was used to determine the levels of tax to be paid. This is where the Nilometer came into play, with priests monitoring the day-to-day level of the river and announcing the awaited arrival of the summer flood.
The simplest Nilometer design is a vertical column submerged in the waters of the river, with marked intervals indicating the depth of the water. One that follows this simple design, albeit housed in an elaborate and ornate stone structure, can still be seen on the island of Rhoda in central Cairo (30.0069°N 31.2250°E). This Nilometer visible today dates as far back as AD 861, when the Abbasid caliph al-Mutawakkil ordered its construction, overseen by the astronomer Alfraganus. It was built on a site occupied by an earlier specimen which was seen by the Syrian Orthodox patriarch Dionysius of Tel Mahre in 830. This prior Nilometer had been ordered in AD 715 by Usama b. Zayd b. Ê¿Adi, who was in charge of collecting the land tax (kharaj) in Egypt for the Umayyad caliph Sulayman ibn Ê¿Abd al-Malik.
While Nilometers originated in Pharaonic times, they continued to be used by the later civilizations that held sway in Egypt. Some were constructed in Roman times.
In the 20th century, the Nile's annual inundation was first greatly reduced, and then eliminated entirely, with the construction of the Aswan dams. While the Aswan High Dam's impact on Egypt and its agriculture has been controversial for other, more complex reasons, it has also had the additional effect of rendering the Nilometer obsolete.