Get to know HYDROELECTRIC POWER

http://en.wikipedia.org/wiki/Hydroelectricity

the production of electrical power through the use of the gravitational force of falling or flowing water.

Hydropower provides about 96 percent of the renewable energy in the United States.

http://www.usbr.gov/power/edu/pamphlet.pdf

http://en.wikipedia.org/wiki/Hydroelectricity