Hydroelectric Dams

Hydropower is one of the oldest sources of energy. It was used thousands of years ago to turn a paddle wheel for purposes such as grinding grain. Hydroelectricity is electricity generated by hydropower, i.e., the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy, accounting for about 20 percent of the world's electricity.  Dams built to generate power are among the most impressive structure built by humans, and they can have large social and environmental impacts.