Untitled Page

Using the Earth's resources, they have developed technologies that have benefited mankind, and helped to sustain and increase the quality of life for all of God's creatures.

Arch dams are constructed with one or more arches pointing upstream. Stability is obtained by a combination of arch and gravity. They are often built across a narrow canyon with sidewalls composed of sound rock where some of the water pressure is transferred to its walls. The extremely well known Hoover dam, built in 1936, is a combination of arch and gravity.

The Earth is amazingly interesting, and throughout the history of the world, mankind has had the intelligence to explore and continually make new technological discoveries..............

Search
Theworldfromhere.com

Newsletter
Sign Up

One of such technological developments is dams. Dams are massive barriers built across rivers and streams to confine and utilize the flow of water for human purposes--other structures such as floodgates or levees are used to protect land from water flow. Dams serve the primary purpose of retaining water, and are among the earliest known man-made structures. They were built for the generation of hydroelectricity, flood control, power generation, irrigation, fish and waterfowl habitat, urban water reservoirs, livestock watering, improvements and recreation.

One of the earliest recorded dams is believed to be a masonry structure 15m-high; built across the Nile River in Egypt c 2900 BC. The Quatinah barrage in modern day Syria is believed to be the oldest standing and surviving dam in the world. It is assumed that the dam dates back to the reign of the Egyptian Pharaoh Sethi, and was enlarged in the Roman period and again between 1934 and 1938. To this day, it still supplies water to the city of Homs.

While dams are formed by human agency; dams can also be formed through natural causes, and even by the intervention of wildlife; such as beavers. Beavers create dams primarily out of mud and sticks to flood a particular habitable area. By flooding a parcel of land, beavers can navigate below or near the surface and remain relatively well hidden or protected from predators. The flooded region also allows beavers access to food--especially during the winter.

Dams are defined by the size. For instance, international standards define large dams as being higher than 15-20 meters, and dams defined as major, are 150-250 meters in height. The tallest dam in the world is the Nurek Dam in Tajikistan--at 300 meters high.

Posted: January 18th, 2010

Resources: Arch.mcgill.ca,
Daviddarling.info/encyclopedia
Answers.com, An.wikipedia.org

When dams are constructed, it is vital that they be built strong; able to hold back water, withstand ice, silt, pressures and stresses from temperature changes and earthquakes. The sites that dams are built on must have stable earth or rock that will hold up and not allow water to seep under the dam. Based on the structure and the material used, dams are classified as Arch dams, Gravity dams, and Embankment or Masonry dams.

Gravity dams hold back water by its own weight and may be solid sloping down stream with a thick base, or buttressed; sloping upstream and strengthened by buttresses, which transfer the dead weight sideways, and require less concrete. Stability is secured by making the dam of such a size and shape that it will resist overturning, sliding and crushing at the toe.

Embankment (earth fill) or Masonry dams are large barriers of rock, sand, silt, or clay for controlling broad streams. Their weight deflects the horizontal water thrust downward toward the broad base. The materials may be uniformly mixed or there may be zones or waterproof material such as concrete; either on the upstream or inside the dam.

One of the best places for building a dam is a narrow part of a deep river valley--the river valley sides can then act as a natural wall for the dam. The primary function of the dam's structure is to fill the gap in the natural reservoir line left by the stream channel. The sites are usually those where the gap becomes a minimum for the required storage capacity.

The Three Gorges, in China; the Fort Peck, in the United States; The Ataturk Dam, in Turkey; The Verzasca Dam, in Switzerland; and The Srisailam Dam, in India, are among the largest dams in the world.