Water, like wind, has been used to do work throughout history. The ancient Greeks used it to power gristmills, and by 610 AD the Japanese used it in several ways.
The world's first hydrogenerating facility was built in Appleton, Wisconsin, in 1882. Use of
hydroelectric power expanded in the US, and it met 60% of the nation's power needs by 1900. President Franklin Roosevelt launched a series of projects that built dams and gained massive amounts of power from them.Today, one-fourth of the electricity used throughout the world is generated with hydroelectric power. In total, hydroelectric power meets 5% of the global demand for energy.
Hydroelectric power is used worldwide. Even in the Third World, large dams are being constructed as a quick rate. Some people are voicing concern that the new dams are increasing too quickly and threatening the local environment as a result.
Some promoters of hydroelectric power view it positively because unlike fossil fuels it does not produce large amounts of pollution. However, critics point to the fact that dams have destroyed habitats and caused tremendous amounts of flooding.
Because hydroelectric power is a new and unknown technology, the potential for a disaster is considerable. The surrounding environment could be destroyed, and thousands could die. The dams are also very big and very
costly, though in the future, small "micro-hydro" generators may become more common.
Nevertheless, many dams are being constructed and used to generate power. In 1986, Venezuela built the world's largest dam at a cost of over US $10 billion. The plant will provide as much energy as 10 large nuclear power plants would.
US DOE Hydropower Program