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Definition: dam from Philip's Encyclopedia

Barrier built to confine water (or check its flow) for irrigation, flood control or electricity generation. The first dams were probably constructed by the Egyptians 4,500 years ago. Gravity dams are anchored by their own weight. Single-arch dams are convex to the water they retain, supported at each end by river banks. Multiple-arch and buttress dams are supported by buttresses rooted in the bedrock. The cheapest commercial source of electricity comes from hydroelectric projects made possible by dams, such as the Aswan High Dam, Egypt.


dam

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Structure built across a river to hold back a body of water (called a reservoir) in order to prevent flooding, provide water for irrigation and storage, and provide hydroelectric power . The biggest dams are of the earth- and rock-fill type, also called embankment dams. Such dams are generally built on broad valley sites. Deep, narrow gorges dictate a concrete dam, where the strength of reinforced concrete can withstand the water pressures involved. Concrete dams A valuable development in arid regions, as in parts of Brazil, is the underground dam , where water is stored on a solid rock base, with a wall to ground level, so avoiding rapid evaporation. Many concrete dams are triangular in cross section, with their vertical face pointing upstream. Their sheer weight holds them in position, and they are called gravity dams . They are no longer favoured for very large dams, however, because they are expensive and time-consuming to build. Other concrete dams are built in the shape of an…
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Full text Article dam

From The Columbia Encyclopedia
barrier, commonly across a watercourse, to hold back water, often forming a reservoir or lake; dams are also sometimes used to control or contain rockslides, mudflows, and the like in regions where these are common. Dams are made of timber, rock, earth, masonry, or concrete or of combinations of…
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Full text Article Dams

From Encyclopedia of 20th Century Technology Full text Article Thematic List of Entries
Construction at Glen Canyon Dam, Colorado River...
For thousands of years, dam and water storage technologies have allowed civilizations to flourish in parts of the world where dry climates would otherwise limit human settlement. As early as 3000 BC, civilizations along the Tigris, Euphrates, Ganges, and Nile Rivers constructed earth and stone dams…
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Full text Article dam

From Britannica Concise Encyclopedia
Barrier built across a stream, river, or estuary to conserve water for such uses as human consumption, irrigation, flood control, and electric-power generation. The earliest recorded dam is believed to be a masonry structure 49 ft (15 m) high built across the Nile River in Egypt c. 2900 bce . Modern…
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Full text Article dam

From The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide
Structure built across a river to hold back a body of water (called a reservoir) in order to prevent flooding, provide water for irrigation and storage, and provide hydroelectric power . The biggest dams are of the earth- and rock-fill type, also called embankment dams. Such dams are generally built…
| 812 words
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Full text Article dams

From Environmental History and Global Change: A Dictionary of Environmental History
Dams have been used to control water flow for agriculture and other purposes since the first farming communities in the Near E. They are first recorded from the Nile valley C. 3000 BC . In China by the C2 BC earth dams 30 m high were being built. In medieval and later times in Europe they were…
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Full text Article Dams

From 1001 Inventions: The Enduring Legacy of Muslim Civilization
Dams are some of the largest civil engineering structures ever built and they play a vital role in civilization. Without dams, more floods would ravage lands, irrigation would not have been as large-scale, and we would not have hydroelectric plants pumping out power today. Arch dams, buttress dams, …
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Full text Article Hoover Dam

From The Columbia Encyclopedia
726 ft (221 m) high and 1,244 ft (379 m) long, on the Colorado River between Nev. and Ariz.; one of the world's largest dams. Built between 1931 and 1936 by the U.S. Bureau of Reclamation, the dam is named for President Herbert Hoover ; from 1933 to 1947 it was known as Boulder Dam. A key unit on…
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Full text Article Hoover Dam

From The Oxford Encyclopedia of the History of American Science, Medicine, and Technology
On the Colorado River southeast of Las Vegas, Hoover Dam, ranked as one of America's “seven modern civil engineering wonders” by the American Society of Civil Engineers, was dedicated 30 September 1935 by President Franklin D. Roosevelt. The dam's ideological origins lie in the Progressive Era's…
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Full text Article Hoover Dam

From Encyclopedia of American Studies
Hoover Dam. 2004. Marcin Klapczynski,...
The earliest European explorers claimed the Colorado River as the spine of life for Arizona and much of the semiarid western United States. They could not have foreseen the hydraulic society that later took shape around this river, but they knew that civilization's success there relied on the…
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The Aswān Dam was the cornerstone of Gamal Abdel Nasser's program for Egyptian economic development. Nasser described the project as “more magnificent and seventeen times greater than the Pyramids.” The dam was to improve the living standard for Egyptians by increasing agricultural output and…
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