Hydroelectricity.orHydroelectric power,is a form of hydropower that uses the energy released as a result of water falling,or flowing downhill or by wave-differences,under the influence of gravity to produce electricity.Specifically,the mechanical energy of the flowing or waving water is converted to electrical energy by a water turbine generator.Hydroelectric power is usually generated at dams or other places where water descends from a height like coasts with a high tides difference.Hydroelectricity is a renewable energy source,since the water that flows in rivers has come from precipitation such as rain or snow and waves in the sea,or even ocean,are moon related.

WORDS:
Hydroelectricity 水电 release 释放 downhill 向下的 convert 转变
turbine generator 涡轮发电机 generate 产生（于） descend ...下来 tide 潮汐
precipitation 蒸发