Hydroelectricity is the production of electrical power through the use of the gravitational force of falling or flowing water.Hydroelectricity capacity is around 800 GW accounting for almost 20% of the global electricity capcity.China and Canada have the largest hydro capacities in the world.If you consider Hydropower as renewable energy,then Hydro is the most widely used renewable energy in the world.In fact Hydroelectricity is the 3rd biggest source of electricity in the world after coal and oil/gas.Hydroelectricity power plants can have massive capacities with the Three Gorges Dam in China being the world’s largest at 22.5 GW.The Itiapu and Guri Dams in South America are the 2nd and 3rd largest with 14 GW and 10 GW capacities.China is set to double its massive hydroelectric capacity to almost 400 GW by 2020 from 20 GW currently.The advantages of Hydroelectricity are many