Dam

A dam is a large wall or barrier that blocks or stops the flow of water, forming a reservoir or a lake. Most dams have a section called a spillway or weir over 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 in Tajikistan. Fish ladders are usually added to dams to allow fish to cross over.

History

Some of the first dams were built in Mesopotamia up to 7,000 years ago. Modern dams are built with arched walls of steel 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 prevent flooding. Other countries build dams to generate electricity using hydroelectric turbine generators. Other countries use dams to store water for use in irrigation (for farming) or drinking by people.

• 

  Arch dam in Turkey.

• 

  Three Gorges Dam, China

• 

  Aswan High Dam in Egypt.

• 

  Srisailam Dam in India.

Dam Media

• 

  The Edersee Dam in Hesse, Germany

• 

  The Dujiangyan irrigation system was initially constructed during the Qin dynasty, around 256 BC.

• 

  The Roman dam at Cornalvo in Spain has been in use for almost two millennia.

• 

  Remains of the Band-e Kaisar dam, built by the Romans in the 3rd century AD

• 

  14th c. Shāh Abbās arch dam

• 

  An engraving of the Rideau Canal locks at Bytown

• 

  The Hoover Dam by Ansel Adams, 1942

• 

  Gordon Dam, Tasmania, is an arch dam.

• 

  Daniel-Johnson Dam, Quebec, is a multiple-arch buttress dam.

• Dam in Europe at Autumn as viewed from FPV drone.