The United States is second with nearly 1500 sites. The largest hydroelectric complex in the world is on the Parana River, between Paraguay and Brazil. Called the Itaipu Dam, its 18 turbines produce 12,600 MGWs of electricity. This power is definitely making an impact in society, but potentially far from being established. Hydroelectric power is obtained by the building of dams or the use of water wheels, to control the flow of water necessary to power a generator.
Hydroelectric dams seem very complicated but are actually simple machines.
A dam holds back water creating a reservoir of potential power. On the upper side of the dam water surges through a tunnel, created by an open water gate, leading to turbines. The water then turns the turbines, which in turn spin generators to create electricity. The water wheel is one of the oldest known sources of power. In the horizontal water wheel, water flows from an aqueduct, and the forward action of the water turns the wheel.