Hydroelectricity is generated by the force of falling water. In hydroelectric power plants, water is stored in a dam and then released through a turbine. The force of the water turns the turbine, which generates electricity. The amount of electricity generated depends on the amount of water flowing through the turbine and the height of the dam. The water is then returned to the river downstream. Hydroelectricity is a renewable source of energy, as long as the water supply is maintained.