Hydroelectricity involves extracting energy from water flowing from a higher altitude to a lower altitude and converting it into electricity. Hydroelectricity has been used as a source of electricity for many years and is now the primary renewable energy resource in America. Hydropower is the most reliable and efficient of all renewable energy sources. “And today, about seven percent of all electricity is generated from hydropower” (DOE.org) The Tennessee Valley Authority is the nation's largest federally-owned electric utility. TVA also owns fossil fuel, nuclear and hydroelectric power plants. “TVA maintains 29 conventional hydroelectric dams throughout the Tennessee river system and a pumped storage facility for electricity generation. » (tva.gov) “Together, these plants produced approximately 13.9 million megawatt hours of electricity in 2004, enough electricity to power nearly a million homes for a year. » (tvakids.com)A hydroelectric power station consists of a dam and a power station. The dam holds water in a reservoir, which resembles a small lake, and the power plant surrounds the turbines and generators that produce electricity. When electricity is needed, water is drained from the tank through a large pipe and into a turbine connected to a generator which, in turn, spins, producing electricity. After passing through the turbine, the water returns to the river downstream of the dam. (Figure 1.1 shows a typical hydroelectric plant) (Wikipedia.com) There are three types of hydroelectric plants: impoundment, diversion, and pumped storage. The size of these plants varies from small to larger systems. A reservoir hydroelectric plant is the most common type and uses a dam to store water from a river in a reservoir. The water is then released from the reservoir middle of paper......to open the Tennessee River to navigation when TVA opened in 1933, but the dams brought the added benefit of production of low cost electricity. . TVA's hydroelectric plants operate with a high degree of reliability and efficiency. Two ongoing projects will further improve the operation of the plant: The Hydroelectric Modernization Project, scheduled for completion around 2015, will significantly increase the hydroelectric system's electricity production. The automation project, which allows plants to be controlled and monitored from a command center in Chattanooga, Tennessee, will reduce operating costs and increase efficiency. These efforts continue to reduce costs, improve efficiency and improve production. In conclusion, hydropower is an efficient and reliable reusable energy source. I believe TVA helped pave the way to show this to people all over the United States..