This river is the maker of the oldest civilization recorded by the historical sources: 5,000 years ago, the Egyptian state emerged on its banks.
It is best known as the longest river on the planet. Nile is consensually considered so as it has 6,695 km in length, even if some say that Amazon is longer (6,800 km). The problem is that nobody could tell where Amazon ends, due to its huge mouth.
Anyway, while Amazon is the mightiest river on the planet (with a debit of 200,000 cubic meters/second, 20 % of the freshwater volume penetrating the oceans), Nile has a 60 times lower debit, as it does not receive any affluent on its last 2.400 km (1.500 mi). Moreover, the Nile's debits fluctuate a lot, as it receives the most abundant waters during the rainfall on the Ethiopian Plateau.
But the role played by the Nile in human life and history is much more important.
The Nile starts from molten snow and rainfall, which make torrents like Mobuku and Semliki in the Ruwenzori Mountain (a glacier-covered equatorial mountain, with a maximum height of 5,119 m / 17,633 ft). Semliki enters Lake Albert. Another southern source is located in Burundi, at a height of 2,050 m (6,830 ft): Kasumo. Then, from the large Lake Victoria, the Nile starts under the name Kagera for emptying itself into the Mediterranean, on the place where 2,300 years ago Alexander the Great founded the famous city of Alexandria. The river crosses Burundi, Uganda, Sudan and Ethiopia before entering Egypt.
From Lake Victoria, the Nile starts through cascades that are 4 m (13 ft) tall and 150 m (500 ft) wide. The Nile enters Lake Kyoga, which acts like a sponge. Further, two granite bars make a strait, just 6 m (20 ft) wide, making the Nile fall from 40 m (133 ft), forming the Murchinson Falls.
Further on, the Nile enters Lake Albert and from this lake, it heads northward. The Nile is swift in this portion, being called Bahr-el-Gebel (the river of the mountains). Then, the Nile crosses a huge area
of swamps, called "Sadd" (halt) by the Arabs. This is a world dominated by papyrus twice the height of a man. The area is as large as the Sargasso Sea and is difficult for navigation.
After 750 km (480 mi), with the No Lake, the world of the swamps has ended. Until the confluence with the Blue Nile, the proper Nile is called the White Nile (Bahr-el-Abiad). The river has lost much of its forces in the swamps as much of its waters evaporate here. But it is strengthened by Sobat River, an affluent coming from Ethiopia. It is so large now that the Arabs call it "Bahr" (sea).
The river has crossed 2,600 km (1,650 mi) and the landscape along its banks turns gradually from steppes to desert, while "Black Africa" turns into the world of the Islam. After the dam Gebel Aulia, the Nile approaches Khartoum, where it will be joined by the Blue Nile. There are more 3,000 km (1,900 mi) to the Mediterranean.
The Blue Nile has 1,500 km (900 mi) and its source is in Sakala (Ethiopia), a sacred place for the Ethiopian Christians. After emerging at the height of 2,900 m (9,660 ft), it crosses Lake Tana (at 1,760 m (5,860 ft). From Lake Tana, the river crosses various cascades. In Sudan it is called Bahr-elAzrak (ashy river).
The two Niles join after the second bridge of Khartoum. The Blue Nile comes with a daily debit of 141 million cubic meters of water, representing 80 % of the total debit of the Nile. The river is called after the confluence Bahr-el-Nil.
In Karthoum, Nile receives also its last affluent: Atbara River, coming filled with mud (varying from red to green) from the Ethiopian Plateau. Now the Nile is 2-4 km (1.2-2.4 mi) wide and is spotted with islands.
Through the desert crossed by the Nile, vegetation growth is restricted at a fringe of about 1.5 km (1 mi) along the river's banks and life is concentrated on a strip few km wide alongside the banks. From Khartoum, the Sudanese capital, to Assouan, 6 cataracts are found on the Nile. The first cataract is located 200 km (125 mi) north of Khartoum. On the fifth cataracts, papyrus beds, gone from Egypt since the time of the pharaohs, can still be seen.
This portion in northern Sudan is the area were the ancient kingdom of Nubia flourished. For a while, even Egypt was ruled by Black Nubian pharaohs.
One of the longest reservoirs on Earth was built at Assouan on the Nile from 1958 to 1970: Lake Nasser, which is 550 km (344 mi) long and with a maximum width of 35 km (22 mi). The reservoirs lay between Egypt (mostly) and Sudan, and required the removal of the temples of Abu Simbel to a 64 m (213 ft) higher place.
The Nile made possible the development of the oldest state known, Egypt, in the middle of the Sahara desert, one of the toughest on Earth. But the Egyptian civilization thrived on its banks 10,000 years ago, while the Egyptian empire rose 5,000 years ago.
12,000 years ago the Nile was much stronger, crossing a savanna, where nowadays we see only dry desert, and receiving numerous strong affluents on its course. But 10,000 years ago the drought was already felt.
6,000 years ago, two cultures were known in Egypt: the Merimde Culture in the north, around Nile's Delta and Badarian Culture in the middle Egypt, around the city of Asyut. From the union of these two cultures, the first great nation-state in the history rose, flourishing for three millennia and leaving us awesome monuments, like the monumental pyramids at the Abu Simbel, Karnak, Philae.
The agriculture in the Nile Valley was strictly connected to the annual flooding, which occurred between July and September, covering huge areas. The inundations meant the Egyptian agriculture did not require irrigations. Still, some crops required stocking water and irrigation.
Of course, the Nile was for the Egyptians the backbone of their unity and the main transport route. The Nile allowed a centralization of the political, military and economical power that permitted the emergence of a huge trained work power necessary for the building of the huge monuments, priceless values of the human civilization.
Due to the steady food supply provided by the fertilizing Nile, Egypt was one of the most stable ancient states till its conquest by the Romans led by Julius Caesar in 30 B.C.
Even today, Egypt is the most populous country in the Middle East and North Africa, due to Nile that can provide the food (directly and indirectly) for such a large population.
At Cairo, the Nile is just 800 m (0.5 mi) wide. Its meanders are hidden by the high buildings. Many changes have occurred in the last decades: new canals, dams and bridges.
Nile Delta, made by the two mouth of the river, Rosette and Damiette, is a triangle with the side of 200 km (125 mi). 20 million people inhabit this "agricultural lung". The delta is crossed by a network of smaller arms, canals and ditches. From its forking point, the Nile still has to make 500 km (310 mi). The Eastern Nile heads northwards after Zifta dam, avoiding Tantah, a quite contaminated industrial center, but crossing Mansurah, a 200,000 inhabitants city, joining Lake Menzaleh, and then reaching Damiette, a furniture center, before entering the Mediterranean.
The western Nile, after Sa el-Hagar (built over the ancient Sais) encounters the Edfina dam, which protects the fields from the invasion of the sea waters. Still, in the last decades, the salinity of the irrigation waters has risen. Through the palm oases, the branch reaches Rosette, a town turned famous because here the famous hieroglyph basalt stone, used by Champollion to decode the ancient Egyptian hieroglyphs was discovered. Here, at Rosette, the Nile is as wide as in Cairo, with banks invaded by palm trees.