What is Dam ?

Large dams belong to the most expensive investments many governments have ever made

Two dams called Ha-Uar running east-west were built to retain water during the annual flood and then release it to surrounding lands. The lake called "Mer-wer" or Lake Moeris covered 1,700 km2 (660 sq mi) and is known today as Birket Qarun.

Dams Can Put Human Rights at Risk:

Most dams that displace large populations are being built by authoritarian governments. In Burma, China, Colombia, Ethiopia, Guatemala, Sudan and other countries, dam builders have often responded to opposition with serious human rights violations. In the worst dam-related massacre, more than 440 indigenous people were killed to make way for Guatemala’s Chixoy Dam in 1982.

An estimated 2000 billion dollars has been spent on dams since 1950. Due to planning errors, technical problems and corruption, dams experience average delays of 44 percent and cost overruns of 96 percent. Such massive overruns make them uneconomic.

By the mid-late third millennium BC, an intricate water-management system within Dholavira in modern-day India was built. The system included 16 reservoirs, dams and various channels for collecting water and storing it

Examples of Buttress Dam: Bartlett dam (USA) and The Daniel-Johnson Dam (Canada)

Sooner or later reservoirs silt up, and the cost of maintaining dams becomes bigger than their benefits. In the United States, more than 1000 dams have been removed at great cost. When dams are not properly built or maintained, they can break.

Dams Are Expensive:

Large dams belong to the most expensive investments many governments have ever made. An estimated 2000 billion dollars has been spent on dams since 1950. Due to planning errors, technical problems and corruption, dams experience average delays of 44 percent and cost overruns of 96 percent. Such massive overruns make them uneconomic

In the world’s biggest dam disaster, the failure of China’s Banqiao Dam killed an estimated 171,000 people in 1975.

One of the engineering wonders of the ancient world was the Great Dam of Marib in Yemen. Initiated somewhere between 1750 and 1700 BC, it was made of packed earth – triangular in cross section, 580 m (1,900 ft) in length and originally 4 m (13 ft) high – running between two groups of rocks on either side, to which it was linked by substantial stonework

steel dam consists of a steel framework, with a steel skin plate on its upstream face. Steel dams are generally of two types: (i) Direct-strutted steel dams, and (ii Cantilever type steel dams.

Dams Don’t Last Forever:

Sooner or later reservoirs silt up, and the cost of maintaining dams becomes bigger than their benefits. In the United States, more than 1000 dams have been removed at great cost. When dams are not properly built or maintained, they can break. In the world’s biggest dam disaster, the failure of China’s Banqiao Dam killed an estimated 171,000 people in 1975.

In 2012, governments and businesses installed 75 gigawatt of wind and solar power, compared with 30 gigawatt of hydropower. Such alternatives fare even better when social and environmental impacts and transmission costs are included.

In a direct strutted steel dam, the water pressure is transmitted directly to the foundation through inclined struts.

Repairs were carried out during various periods, most important around 750 BC, and 250 years later the dam height was increased to 7 m (23 ft). After the end of the Kingdom of Saba, the dam fell under the control of the Ḥimyarites (~115 BC) who undertook further improvements, creating a structure 14 m (46 ft) high, with five spillway channels, two masonry-reinforced sluices, a settling pond, and a 1,000 m (3,300 ft) canal to a distribution tank.

Better Solutions Are Usually Available:

In 2012, governments and businesses installed 75 gigawatt of wind and solar power, compared with 30 gigawatt of hydropower. Such alternatives fare even better when social and environmental impacts and transmission costs are included. The International Energy Agency has proposed that 60 percent of the funds needed to achieve energy access for all should go to local renewable energy projects.

The International Energy Agency has proposed that 60 percent of the funds needed to achieve energy access for all should go to local renewable energy projects.

In a cantilever type steel dam, there is a bent supporting the upper part of the deck, which is formed into a cantilever truss. This arrangement introduces a tensile force in the deck girder which can be taken care of by anchoring it into the foundation at the upstream toe

These extensive works were not actually finalized until 325 AD and allowed the irrigation of 25,000 acres (100 km2).

Hovey suggested that tension at the upstream toe may be reduced by flattening the slopes of the lower struts in the bent. However, it would require heavier sections for strut

Eflatun Pınar is a Hittite dam and spring temple near Konya, Turkey. It is thought to be from the time of the Hittite empire between the 15th and 13th century BC.

A dam is a large wall or barrier that obstructs or stops the flow of water, forming a reservoir or a lake. Most dams have a section called a spillway or weir over which, or through which, water flows, either sometimes or always. Dams generally serve the primary purpose of retaining water. The tallest dam in the world is the 300 meter high Nurek Dam in Tajikistan.

Dams are structural barriers built to obstruct or control the flow of water in rivers and streams. They are designed to serve two broad functions. The first is the storage of water to compensate for fluctuations in river discharge (flow) or in demand for water and energy

Another alternative to reduce tension is to frame together the entire bent rigidly so that the moment due to the weight of the water on the lower part of the deck is utilised to offset the moment induced in the cantilever.

The word dam can be traced back to Middle English, and before that, from Middle Dutch, as seen in the names of many old cities.