NILE FLOODS
    Since ancient times, the River Nile has flooded every year. The floods spread fertile mud over the land helping farmers to grow their crops. But often big floods destroyed homes and farmland. At other times of the year there was drought.

CONTROLLING THE NILE
    In 1902 engineers built a dam just south of Aswan to control the floods. This dam was made higher in 1912 and again in 1933. But this first Aswan Dam was still not enough to control the Nile fully.

    Building work started on the Aswan High Dam in 1960. The dam is made of earth and granite rock-fill, with a core of clay and cement. It is over 3.6 kilometers wide, 111 meters high and 40 meters thick at the too. At its base on the river bed it is a massive 925 meters thick. The dam took ten years to build.

LAKE NASSER
    Aswan High Dam was officially opened in 1971. During the rainy season, the dam holds back the Nile's rising waters. As the waters rose behind the dam, they gradually formed a reservoir more than 500 kilometers long. The new reservoir was called Lake Nasser after the Egyptian president.

CREATING THE LAKE
    Around 50,000 people had to leave their homes to make way for the reservoir. They were taken to a new farming region 50 kilometers north of Aswan. Several ancient temples and islands were flooded, but some were rescued. In a huge-scale operation, the temples of Ramses II and Nefertari were cut into 30-tonne blocks and put together again, piece by piece on hills overlooking the river. This difficult work took four years. Other small temples were also moved from an island in the Nile which was to be totally submerged.

BENEFITS
    The water stored in Lake Nasser is used to irrigate farmland during dry periods and throughout the year. More crops can now be grown every year, producing more food to feed the growing population. As the water pours through the dam, it also drives turbines, which generate half of Egypt's electricity.

PROBLEMS

This human attempt to control nature has brought many problems as well as benefits. The dam stops fertile mud from moving downstream. So that farmers have to use more chemicals to fertilize their land. Since the dam was built, there has also been an increase in a disease carried by tiny worms in the Nile's water snails. Yearly floods used to keep the numbers of snails down. A rise in the water table has also brought salts to the surface, which makes the land infertile.