A dam is a barrier that impounds water and serve a purpose of retaining water for irrigation and control water flow or flood. The first dams were built in Mesopotamia up to 7,000 years ago. Dams in modern days were built with arched walls of steel rod-reinforced concrete.
The arched wall is a strongest shape to withstand the great weight and pressure done by water. Dams also serve the main purpose of generating hydroelectricity.
The dam generated by releasing water pressured behind the dam forces the by water down pipes that lead to a turbine, this causes the turbine to turn, which turns a generator which makes electricity. The benefits of hydroelectricity are can be made very quickly less pollution and generate large amount of electricity in a cheap price. Sirindhorn dam is the example of dam which generating hydroelectricity in Thailand.