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In the middle of the arid Egyptian desert lies one of the largest embankment dams in the world. It is called the Aswan High Dam, or Saad el Aali in Arabic, and it captures the mighty Nile River in the world's third largest reservoir, Lake Nasser. Before the dam was built, the Nile River overflowed its banks once a year and deposited four million tons of nutrient-rich silt on the valley floor, making Egypt's otherwise dry land productive and fertile. But there were some years when the river did not rise at all, causing widespread drought and famine. In 1952, Egyptian president Gamal Abdal-Nasser pledged to control his country's annual flood with a giant new dam across the Nile River. His plan worked.

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The Aswan High Dam captures floodwater during rainy seasons and releases the water during times of drought. The dam also generates enormous amounts of electric power -- more than 10 billion kilowatt-hours every year. That's enough electricity to power one million color televisions for 20 years!

Unfortunately, the dam has also produced several negative side effects. In order to build the dam, 90,000 Egyptian peasants had to move. To make matters worse, the rich silt that normally fertilized the dry desert land during annual floods is now stuck at the bottom of Lake Nasser! Farmers have been forced to use about one million tons of artificial fertilizer as a substitute for natural nutrients that once fertilized the arid floodplain.

Aswan High Dam 5.97 trillion cubic feet