This creates electricity. Hydroelectric power is produced as water passes through a dam, and into a river below. The more water that passes through a dam, the more energy is produced. Once a dam is built, an artificial man-made lake is created behind the dam. Electricity is produced by a device called a turbine.
Turbines contain metal coils surrounded by magnets.
When the magnets spin over the metal coils, electricity is produced. Turbines are located inside dams. The falling water spins the magnets. Dams provide clean, pollution free energy, but they can also harm the environment. Species that use rivers to spawn are often hurt by dams.