Difference between revisions of "Aswan Dam" - New World Encyclopedia
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==History== | ==History== | ||
[[Image:High Dam Burg Closeup, Aswan, Egypt, Oct 2004.jpg|thumb|left|A closeup view of the Soviet-Egyptian friendship monument]] | [[Image:High Dam Burg Closeup, Aswan, Egypt, Oct 2004.jpg|thumb|left|A closeup view of the Soviet-Egyptian friendship monument]] | ||
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| − | + | The Nile River has been a focus of enginneering interest since the late part of the 19th century. It had long been thought that a dam in the area would prove highely beneficial for the neighboring communitities and agricultural lands. To this end, British engineers began work ont eh first Aswan Dam in 1899. Construction continued for three years, but the final product proved to be inadequate for the strong currents of the Nile. In response to the failures of the original dam, the height of the Aswan Dam was raised in 1907, and again in 1929. The two lengthy attempts to raise the height of the dam still proved insufficient to contain the river's flow. The dam almost overflowed in 1946, prompting the authorities to reconsider the future of the old dam. Rather than simply add on to the height of the dam, as had been attempted in the past, the Egyptian authorities decided to built a second dam farther down the river. Construction on the second dam began after the Eyptian Revolution of 1952, when Gamal Abdel Nasser gained political control of the country. The second dam was originally going to be a joint effort between Egypt, the United States, and Great Britain, but the forign backers pulled the funding before construction began. | |
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| + | Without the promised funding from the United States and Great Britain, Egypt was left unable to fully fund the ambitious building project. Recognizing the need for monetary funds, the Soviet Union offered to provide some of the needed funding to gain a foothold in Africa during the cold war. Most historians feel that the Soviet funding of the Aswan Dam is related more towards an attempt to gain a long term foothold in the area, rather than an attempt to gain economically. For the construction, the Soviet Union provided technicians and large amchinery, as well as funds. Construction on the second dam lasted for twenty years, from 1950 to 1970. In an unexpected construction method, the reservoir was allowed to fill with water before construction was officially completed. However, in light of the endemic dryness in the region, the attempt to gather as much water as possible can be easily understood. | ||
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{{wide image|Aswan dam.jpg|1024px|A panorama of Aswan Dam}} | {{wide image|Aswan dam.jpg|1024px|A panorama of Aswan Dam}} | ||
[[Image:Egypt.Aswan.AswanLowDam.01.jpg|right|250px|thumb|Aswan Low Dam]] | [[Image:Egypt.Aswan.AswanLowDam.01.jpg|right|250px|thumb|Aswan Low Dam]] | ||
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==Benefits== | ==Benefits== | ||
Revision as of 18:54, 19 December 2007
The Aswan Dam, located in Aswan Egypr, tames the Nile River and utilizes the power of the River for a variety of social and eonomic causes. There are actually two dams on the NIle River at Aswan, the Aswan High Dam and the Aswan Low Dam, both of which work together to prevent the annual large floods fom the Nile. Previous to the building of the Aswan Dam, the NIle would flood every winter, potentially destroying any crops that were planted in the NIle Valley. For the purpose of this article the two Aswan Dams will be counted as a single dam, due to the fact that their effects are virtually inseperable.
Description
The Aswan Dam is a rock fill dam, a type of dam that relies on compacted dirt for its stability. Unlike a traditional cement dam, a rock fill dam relies on the fricion between small particles of stone and dirt to maintain its stability. Rack fill dams also need to be placed in a solod bedrock of rock for stability.
The traditional elements of a rock fill dam, stone and clay, are the main material elements of the Aswan Dam. The towering edifice extends 111 meters from the ground, to hold back an astonishing 5.97 trillion cubic feet of water. The water that is held back by the Aswan Dam forms the Lake Nasser, a major source for water in the area. The water that is held back by the dam rushes into the reservoir at a maximum of 11,000 m³ of water per second. To allow for the possibility that heavy rainfall could push the maximum flow of the dam, a series of emergency spillways have been built around the dam to safetly process an additional 5,000 m³ per second.
Most of the water that enters into Lake Nasser is slated for agricultural causes, as the area experiences very little annual rainfall. The water from the resevoir is applied to crops on the field through an extensive irrigation system, a system that allows two crops a year to be produced. This is a significant change from traditional farming methods that rely on natural precipitation. When utilizing natural precipitation as the sole source of agricultural water, only one crop a year can be produced. When using artificial irrigation, the crop yield of the area can be doubled, which enhances the economy of the region. Approximately 8 million feddans ( a unit of measurement roughly equivalent to an acre) recieve water from Lake NAsser for irrigation purposes. The agricultural yield of the dam is about an 83& efficiency, which while not high on first glance, is considereably higher than manyother dams built around the world for the same purposes. One flaw in the system of water distribution, however, is the flow of water down the series of branch canals. Many feel that the water flow down the branch canals is not equally distributed. [1]
The irrigation aims of the Aswan Dam are often complicated by the chemical composition of the water flowing down the Nile River. The water that reaches the dam has a saline composition of approximately 0.25 kg/m3, a composition commonly referred to as "sweet water". The levels of salt in the Nile water have allowed for another industry to develop around the Aswan dam: that of salt exportation. Through a series of extraction methods the Egyptian government has been able to export a large amount of salt to the world markets. In 1995, the levels of salt exportation from Egypt were higher than the levels of salt imported, an unusual occurrence for the Egyptian economy. At this time, over 27 million tosn of salt are exported from Egypt, much of which derives from the Aswan Dam.
History
The Nile River has been a focus of enginneering interest since the late part of the 19th century. It had long been thought that a dam in the area would prove highely beneficial for the neighboring communitities and agricultural lands. To this end, British engineers began work ont eh first Aswan Dam in 1899. Construction continued for three years, but the final product proved to be inadequate for the strong currents of the Nile. In response to the failures of the original dam, the height of the Aswan Dam was raised in 1907, and again in 1929. The two lengthy attempts to raise the height of the dam still proved insufficient to contain the river's flow. The dam almost overflowed in 1946, prompting the authorities to reconsider the future of the old dam. Rather than simply add on to the height of the dam, as had been attempted in the past, the Egyptian authorities decided to built a second dam farther down the river. Construction on the second dam began after the Eyptian Revolution of 1952, when Gamal Abdel Nasser gained political control of the country. The second dam was originally going to be a joint effort between Egypt, the United States, and Great Britain, but the forign backers pulled the funding before construction began.
Without the promised funding from the United States and Great Britain, Egypt was left unable to fully fund the ambitious building project. Recognizing the need for monetary funds, the Soviet Union offered to provide some of the needed funding to gain a foothold in Africa during the cold war. Most historians feel that the Soviet funding of the Aswan Dam is related more towards an attempt to gain a long term foothold in the area, rather than an attempt to gain economically. For the construction, the Soviet Union provided technicians and large amchinery, as well as funds. Construction on the second dam lasted for twenty years, from 1950 to 1970. In an unexpected construction method, the reservoir was allowed to fill with water before construction was officially completed. However, in light of the endemic dryness in the region, the attempt to gather as much water as possible can be easily understood.
Benefits
The dam powers twelve generators each rated at 175 megawatts, producing a hydroelectric output of 2.1 gigawatts. Power generation began in 1967. When the dam first reached peak output it produced around half of Egypt's entire electricity production (about 15% by 1998) and allowed for the connection of most Egyptian villages to use electricity for the first time. The dam mitigated the effects of dangerous floods in 1964 and 1973 and of threatening droughts in 1972–73 and 1983–84. A new fishing industry has been created around Lake Nasser, though it is struggling due to its distance from any significant markets.
Environmental and cultural issues
Damming the Nile caused a number of environmental issues. It flooded much of lower Nubia and over 90,000 people were displaced. Lake Nasser flooded valuable archaeological sites. The silt which was deposited in the yearly floods, and made the Nile floodplain fertile, is now held behind the dam. Silt deposited in the reservoir is lowering the water storage capacity of Lake Nasser. Poor irrigation practices are waterlogging soils and bringing salt to the surface. Mediterranean fishing declined after the dam was finished because nutrients that used to flow down the Nile to the Mediterranean were trapped behind the dam.
There is some erosion of farmland down-river. Erosion of coastline barriers, due to lack of new sediments from floods, will eventually cause loss of the brackish water lake fishery that is currently the largest source of fish for Egypt, and the subsidence of the Nile Delta will lead to inundation of the northern portion of the delta with seawater, in areas which are now used for rice crops. The delta itself, no longer renewed by Nile silt, has lost much of its fertility. The red-brick construction industry, which used delta mud, is also severely affected. There is significant erosion of coastlines (due to lack of sand, which was once brought by the Nile) all along the eastern Mediterranean.
The need to use artificial fertilizers supplied by international corporations is controversial too, causing chemical pollution which the traditional river silt did not. Indifferent irrigation control has also caused some farmland to be damaged by waterlogging and increased salinity, a problem complicated by the reduced flow of the river, which allows salt water to encroach further into the delta.
Mediterranean fish stocks are also negatively affected by the dam. The eastern basin of the Mediterranean is low in fertility, and traditionally the marine ecosystem depended on the rich flow of phosphate and silicates from the Nile outflow. Mediterranean catches decreased by almost half after the dam was constructed. The dam has been implicated in a rise in cases of schistosomiasis (bilharzia), due to the thick plant life that has grown up in Lake Nasser, which hosts the snails who carry the disease.
The Aswan dam tends to increase the salinity of the Mediterranean Sea, and this affects the Mediterranean's outflow current into the Atlantic Ocean (see Strait of Gibraltar). This current can be traced thousands of kilometers into the Atlantic.
Notes
- ↑ R.J.Oosterbaan, 1999. Impacts of the Irrigation Improvement Projects in Egypt. Egyptian-Dutch Advisory Panel and International Institute for Land Reclamation and Improvement, Wageningen, The Netherlands.
ReferencesISBN links support NWE through referral fees
External links
- Sayed El-Sayed and Gert L. van Dijken 'The southeastern Mediterranean ecosystem revisited: Thirty years after the construction of the Aswan High Dam.'
- Satellite views on Google Maps
- http://maps.google.com/maps?hl=en&ie=UTF8&z=14&ll=24.034001,32.865901&spn=0.056362,0.078535&t=k&om=1
- Info on the Aswan Dam
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