Hydroelectricity is electricity generated by hydropower, which usually requires the potential energy of water stored behind a dam to drive a water turbine and generator. The map shows 632 large dams and 6 major dams. Major dams are defined as being greater than 150 metres in height and large dams as between 10 to 15 metres and 150 metres. Also, mapped are 479 hydroelectric generating stations. A generating station (power plant) is an industrial facility built and operated to generate electricity. Hydroelectric power is generated from a plant in which the turbine generators are driven by falling or flowing water.