Hydropower (from Greek: ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water to produce electricity or to power machines. This is achieved by converting the kinetic energy of water into electrical or mechanical energy. Hydropower is a form of sustainable energy production.
Since ancient times, hydropower from watermills has been used as a renewable energy source for irrigation and the operation of mechanical devices, such as gristmills, sawmills, textile mills, trip hammers, dock cranes, domestic lifts, and ore mills. A trompe, which produces compressed air from falling water, is sometimes used to power other machinery at a distance.Hydropower is an attractive alternative to fossil fuels as it does not directly produce atmospheric pollutants. However, economic, sociological, and environmental downsides limit its use. International institutions such as the World Bank view hydropower as a low-carbon means for economic development.