Dam

Adamis a largewallor barrier that blocks or stops the flow ofwater,forming areservoiror alake.Most dams have a section called a spillway orweirover which, or through which, water flows, either sometimes or always. Dams generally serve the primary purpose of retaining water. The tallest dam in the world is the 300 meter high Nurek Dam inTajikistan.

History

Some of the first dams were built inMesopotamiaup to 7,000 years ago. Modern dams are built witharchedwalls ofsteel rod-reinforced concrete.The arched wall is a very strong shape which helps the wall to withstand the huge weight of the water.

Reasons for building dams

There are a number of reasons that people build dams. Some countries build dams to control the flow of water in the downstream river systems, and preventflooding.Other countries build dams to generate electricity usinghydroelectricturbinegenerators.Other countries use dams to store water for use inirrigation(forfarming) ordrinkingby people.

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  Arch dam inTurkey.
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  Three Gorges Dam,China
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  Aswan High Dam inEgypt.
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  Srisailam Dam inIndia.