The Nile River is the longest river in the world, stretching for 4,187 miles. The Nile flows from south to north and is formed by three major tributaries: the White Nile, the Blue Nile and the Atbara.
The Blue Nile has its source in the highlands of the African country of Ethiopia, by Lake Tana. The runoff from spring rain and melting snow caused the annual summer flood of the Nile that the Egyptians depended on for water to irrigate their crops, and deposit fertile top soil.

Just north of Khartoum the combined White and Blue Nile meet their final major tributary, the Atbara which also has its source in the Ethiopian highlands.

The Nile then plunges into a canyon. Before the construction of the Aswan High Dam; the Nile rolled through a series of six rapids, called cataracts, between northern Sudan and southern Egypt. Since construction of the dam, the river has gradually changed its course.

North of Cairo, the Nile splits into two branches (or distributaries), the Rosetta Branch to the west and the Damietta to the east. Lake Nasser is a man-made lake created by the construction of the Aswan High Dam, opened in 1971. The dam was built to regulate the flow of the Nile River, and thus benefit the region's inhabitants. However, technology often also disrupts a local ecosystem, the life and nature it affects.

The canyon that was once behind where the dam is now, was flooded after the dam was built. Before the region was flooded for the dam, some Ancient sites were carefully moved. Others were permanently covered and destroyed by the water. Lake Nasser stretches over a distance of 312 miles. Gone are the days when Egyptians worry that the Nile will flood too high, destroying their crops; or fall too low, not providing proper irrigation. To enjoy the benefits of a steady river flow, thousands of peoples homes were submerged when the dam went into operation and Lake Nasser was formed.

The Aswan High Dam has caused other changes. The water surface of the lake has reduced the average temperature in the region. The dam has also harnessed the water for the production of electricity and navigation has been improved.
Furthermore, the Nile is no longer flowing strongly enough to keep salt water from the Mediterranean Sea from forcing its way up the Nile.