The term hydropower often suggests giant dams capable of transmitting tens of thousands of cubic feet of water per minute. Such dams are responsible for only about six percent of all the electricity produced in the United States today.
Hydropower facilities do not have to be massive buildings. At one time in the United States--and still, in many places around the world--electrical power is generated at low-head facilities, dams where the vertical drop through which water passes is a relatively short distance and/or where water flow is relatively modest. Indeed, the first commercial hydroelectric facility in the world consisted of a waterwheel on the Fox River in Appleton, Wisconsin. The facility, opened in 1882, generated enough electricity to operate lighting systems at two paper mills and one private residence.
Electrical demand grew rapidly in the United States during the early twentieth century, and hydropower supplied much of that demand. By the 1930s, nearly 40 percent of the electricity used in this country was produced by hydroelectric facilities. In some Northeastern states, hydropower accounted for 55-85 percent of the electricity produced.
A number of social, economic, political, and technical changes soon began to alter that pattern. Perhaps most important was the vastly increased efficiency of power plants operated by fossil fuels . The fraction of electrical power from such plants rose to more than 80 percent by the 1970s.
In addition, the United States began to move from a decentralized energy system in which many local energy companies met the needs of local communities, to large, centralized utilities that served many counties or states. In the 1920s, more than 6,500 electric power companies existed in the nation. As the government recognized power companies as monopolies, that number began to drop rapidly. Companies that owned a handful of low-head dams on one or more rivers could no longer compete with their giant cousins that operated huge plants powered by oil, natural gas , or coal .
As a result, hundreds of small hydroelectric plants around the nation were closed down. According to one study, over 770 low-head hydroelectric plants were abandoned between 1940 and 1980. In some states, the loss of low-head generating capacity was especially striking. Between 1950 and 1973, Consumers Power Company, one of Michigan's two electric utilities , sold off 44 hydroelectric plants.
Some experts believe that low-head hydropower should receive more attention today. Social and technical factors still prevent low-head power from seriously competing with other forms of energy on a national scale. But it may meet the needs of local communities in special circumstances. For example, a project has been undertaken to rehabilitate four low-head dams on the Boardman River in northwestern Michigan. The new facility is expected to increase the electrical energy available to nearby Traverse City and adjoining areas by about 20 percent.
Low-head hydropower appears to have a more promising future in less-developed parts of the world. For example, China has more than 76,000 low-head dams that generate a total of 9,500 megawatts of power. An estimated 50 percent of rural townships depend on such plants to meet their electrical needs. Low-head hydropower is also of increasing importance in nations with fossil-fueled plants and growing electricity needs. Among the fastest growing of these are Peru, India, the Philippines, Costa Rica, Thailand, and Guatemala.
[David E. Newton ]
Lapedes, D. N., ed. McGraw-Hill Encyclopedia of Energy. New York: McGraw-Hill, 1976.
Kakela, P., G, Chilson, and W. Patric. "Low-Head Hydropower for Local Use." Environment (January-February 1984): 31–38.