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The energy supplied by flowing water has been used by humans since shortly before the start of the Christian era: the waterwheel, the geared water mill, and the Vitruvian mill received increased use as civilization developed in the Mediterranean region.

The energy supplied by flowing water has been used by humans since shortly before the start of the Christian era: the [https://en.wikipedia.org/wiki/Water_wheel waterwheel], the [https://en.wikipedia.org/wiki/Watermill geared water mill], and the [https://en.wikipedia.org/wiki/Watermill|History Vitruvian mill] received increased use as civilization developed in the Mediterranean region.

[[file:Uglich hydroelectric power plant, 2010.jpg|thumb|400px|Uglich hydroelectric power plant, Russia. Courtesy [https://commons.wikimedia.org/wiki/File:Uglich_hydroelectric_power_plant,_2010.jpg Wikimedia Commons].]]

[[file:Uglich hydroelectric power plant, 2010.jpg|thumb|400px|Uglich hydroelectric power plant, Russia. Courtesy [https://commons.wikimedia.org/wiki/File:Uglich_hydroelectric_power_plant,_2010.jpg Wikimedia Commons].]]

During the Middle Ages, the use of the geared water mill extended throughout Western Europe, where it was used to grind grain, to saw wood and marble, and to crush metallic ores. Water mills became the base for the beginning of industrial development. Flowing water as a source of energy extended to many other regions of the world in subsequent years.

During the [http://www.history.com/topics/middle-ages Middle Ages], the use of the geared water mill extended throughout Western Europe, where it was used to grind grain, to saw wood and marble, and to crush metallic ores. Water mills became the base for the beginning of industrial development. Flowing water as a source of energy extended to many other regions of the world in subsequent years.

[[file:St54Figure46.JPG|thumb|400px|{{figure number|1}}World hydroelectric power generation and percent of the world's total electricity generation.<ref name+Salvador_2005>Salvador, Amos, Energy-A Historical Perspective and 21st Century Forecast: AAPG Studies in Geology 54, 208 p.</ref>]]

[[file:St54Figure46.JPG|thumb|400px|{{figure number|1}}World hydroelectric power generation and percent of the world's total electricity generation.<ref name+Salvador_2005>Salvador, Amos, Energy-A Historical Perspective and 21st Century Forecast: AAPG Studies in Geology 54, 208 p.</ref>]]

However, it was not until the flow of water was used in the generation of electricity that water started to make a major contribution to the world's supply of energy. Hydroelectric power is, as of 2005, the second largest source of electricity in the world (18%) after coal, which supplies about 38%, but ahead of nuclear power, natural gas, and oil, which contribute 17, 16, and 10%, respectively, of the total generated electricity.

However, it was not until the flow of water was used in the generation of electricity that water started to make a major contribution to the world's supply of energy. Hydroelectric power is, as of 2005, the second largest source of electricity in the world (18%) after [[coal]], which supplies about 38%, but ahead of [[nuclear power]], [[natural gas]], and [[oil]], which contribute 17, 16, and 10%, respectively, of the total generated electricity.

The world's first hydroelectric power plant was built at Godalming, in England, in 1881. Hydroelectric power developed rapidly during the 20th century, even in countries with other abundant sources of energy.

The world's first hydroelectric power plant was built at Godalming, in England, in 1881. Hydroelectric power developed rapidly during the 20th century, even in countries with other abundant sources of energy.

Hydroelectric power was at first believed to be an attractive source of energy, potentially widely distributed around the world, environmentally clean, inexhaustible, efficient, and economically competitive, especially attractive to countries with limited fossil fuel resources. It has been found that this was not always the case.

Hydroelectric power was at first believed to be an attractive source of energy, potentially widely distributed around the world, environmentally clean, inexhaustible, efficient, and economically competitive, especially attractive to countries with limited [[fossil fuel]] resources. It has been found that this was not always the case.

Although dams, not only those built for the generation of electricity but also those designed for flood control, irrigation, water supply, or a combination of these purposes, have delivered significant benefits, they have often been the cause of disastrous social upheavals and major negative environmental impacts, and their construction has serious geographic limitations.

Although dams, not only those built for the generation of electricity but also those designed for flood control, irrigation, water supply, or a combination of these purposes, have delivered significant benefits, they have often been the cause of disastrous social upheavals and major negative environmental impacts, and their construction has serious geographic limitations.