The Nile is the world's longest river at about 4,132 miles (6,650 kilometers). However, it carries less water than many rivers that are far shorter, because little rain falls in the northern part of its basin. The Nile drains about one tenth of the African continent, including parts of the countries of Tanzania, Burundi, Rwanda, Democratic Republic of the Congo, Kenya, Uganda, Ethiopia, Sudan, and Egypt.
The Nile begins at the equator, in the waters of Lake Victoria. In Uganda the river passes through Lake Kyoga and the southern end of Lake Albert. The Democratic Republic of the Congo is on Lake Albert's eastern shore. Stretches of the upper river are called the Victoria Nile and the Albert Nile. As it flows through southern Sudan, the river is called the Mountain Nile. Farther downstream it is known as the White Nile.
At Khartoum in Sudan, the White Nile is joined by the Blue Nile from the east. The Blue Nile flows out of the rainy Ethiopian Plateau and, in the course of a year, contributes more water to the combined stream than the White does, even though the White is a longer river. The heavy rainfall occurs mostly in the summer, causing seasonal flooding downstream.
The highlands of Ethiopia are the source of the Nile's last major tributary, the Atbara. In the desert between Khartoum and southern Egypt are several widely separated areas of rapids known as the cataracts of the Nile. North of Cairo the river fans out and distributes its waters so that they flow into the Mediterranean from more than one stream. This is called a delta system.
Tropical rain forests of coffee shrubs and bamboo, as well as banana, ebony, and rubber trees are found in upper regions in southwestern Ethiopia and the East African Plateau. Savanna grasslands run along the Blue Nile. Papyrus, a reed used since ancient times for making paper, is found in the swampy region of southern Sudan. Desert extends all the way from Khartoum to the Mediterranean. Only a few small shrubs are found in this region.
Several varieties of fish are found in the Nile. These include the Nile perch, catfish, eel, lungfish, mudfish, and tiger fish. Nile perch can grow to 300 pounds (140 kilograms). Such reptiles as the Nile crocodile and the soft-shelled turtle may be found. Among the many snakes of the Nile are two kinds of cobras. The hippopotamus is found in parts of southern Sudan. Harmful insects such as the tsetse fly are found in the upper Nile basin.
Ancient Egyptians planted seeds in mud left by annual floods. Irrigation is now controlled, and more than one crop per year is produced in the fertile soil and warm climate. The main crops are beans, corn, cotton, millet, rice, wheat, and sugarcane.
The Nile River also serves as a main waterway for the transportation of people and goods. The cataracts, however, are an obstacle to navigation.
The valley of the Nile is one of the world's cradles of civilization. Ancient Egyptians who lived on the banks of the river were among the first to develop agriculture and use the plow. Even today, almost 95 percent of Egypt's population lives in the Nile valley and delta, which makes up only 5 percent of Egypt's land.
The ancient Egyptians did not know where their great river came from. Only in about 1860 did the English explorer John Speke identify Lake Victoria as the source.
The Aswan High Dam, 600 miles (960 kilometers) south of Cairo, Egypt, was constructed between 1959 and 1970 for the purposes of controlling floods and producing electric power. Behind the dam, the backed-up waters of the river form Lake Nasser. The formation of the lake left ancient monuments underwater. Because of the dam, much of the river mud needed to keep the Nile Valley fertile now settles on the floor of the lake. As a result, farmers must use increasing amounts of artificial fertilizers, which flow into and pollute the river. Also, not enough mud is now being deposited upon the rich delta land to replace what the Mediterranean Sea wears away. As a result, the delta is shrinking.
