When it rains in the mountains, the water flows into streams and rivers flowing towards the seas. Water that moves or falls can be used for various purposes, including work. Energy is, as you know, the ability to do work, and water in motion has kinetic energy that can be transformed into mechanical work, and thus into electrical energy.

For hundreds of years, moving water has been turning wooden wheels (mill wheels) in mills. This rotation is transmitted to the grinder in which the grains of corn and wheat are crushed into flour. In 1086 the great book “Domesday Book” was written in England. The book, written at the request of William the Conqueror, listed land and real estate ownership for tax purposes. According to that book, there were 5,624 mills in the south of England. About 400 people used one mill. Water can flow over a wooden wheel or under the wheels. If the water flows over a wooden wheel, then the potential energy of the water comes to the fore. In other words, the possibility (potential) of water flowing from a higher height downwards is used. If the water is third under the wheels then the water transfers its kinetic energy to the wheel.

Today, moving water is also used to produce electricity in hydroelectric power plants. Hydro means water, according to the Greek word hydor which means water. Thus, hydropower plants are power plants that convert energy, its potential and kinetic energy, into electricity. The dam in the hydroelectric power plant enables control of the river flow. The dam creates a lake, an accumulation lake, which serves as a reservoir of water. Accumulate means collect. The dam does not necessarily create a reservoir, but can only block the flow of the river to direct the water. In any case, the water flowing into the river is directed through the hydroelectric plant.

The water behind the dam flows through a pipeline and through nozzles (pipes of a special shape) between the blades of the turbine rotor which therefore rotates. The turbine is similar to a propeller, although it looks a little different because it is powered by water that is significantly denser than air.
The turbine rotor rotates the generator rotor to produce electricity.
The produced electricity is transmitted over long distances through the electricity transmission network to homes, factories, offices, schools and other places where it is needed.

Hydropower plants are usually located on rivers in hilly areas, although hydropower plants are sometimes built on large rivers that flow through flatter areas.