Flowing water has energy that can be captured and turned into electricity. This is called hydroelectric power or hydropower.
There are different types of hydroelectric power plant. The most common type uses a dam on a river to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. But hydroelectric power doesn't necessarily require a large dam. Smaller hydroelectric power plants may use a low dam or weir to raise the water level a little; others just use a small canal or penstock to channel the river water through a turbine.
Today's hydropower plants range in size from small, local projects producing a few kilowatts to huge dams and reservoirs that generate 10,000 MW or more and supply energy to millions of people. Although output varies from year to year depending on the amount of precipitation received in upstream watersheds, hydropower is currently the largest source of electricity from renewable resources, generating roughly 10% of the electricity used in the United States.
Read the following for more information: