Difference between revisions of "Aswan Dam" - New World Encyclopedia
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[[Image:Lake Nasser location.png|thumb|right|250px|Map showing reservoir]] | [[Image:Lake Nasser location.png|thumb|right|250px|Map showing reservoir]] | ||
[[Image:Power Station of Aswan dam.jpg|thumb|250px|right|The [[Hydroelectricity|hydroelectric]] power station of Aswan Dam]] | [[Image:Power Station of Aswan dam.jpg|thumb|250px|right|The [[Hydroelectricity|hydroelectric]] power station of Aswan Dam]] | ||
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| − | + | 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. | |
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| − | + | ==Description== | |
| − | The | + | 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. |
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| − | + | 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. | |
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[[image:NileBalance.JPG|thumb|left|Water balances]] | [[image:NileBalance.JPG|thumb|left|Water balances]] | ||
[[image:NileCanals.JPG|thumb|left|Main irrigation system]] | [[image:NileCanals.JPG|thumb|left|Main irrigation system]] | ||
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The salt concentration of the water in the Aswan reservoir is about 0.25 kg/m<sup>3</sup>. This is very "sweet" water. At an annual inflow of 55 billion m<sup>3</sup>, the annual salt import reaches 14 million ton. The average salt concentration of the drainage water evacuated into the sea and the coastal lakes is 2.7 kg/m<sup>3</sup> (Egyptian Drainage Research Institute, yearbook 1995/1996). At an annual discharge of 10 billion m<sup>3</sup> (not counting the 2 billion m<sup>3</sup> of salt intrusion from the sea and the lakes, see figure "Water balances"), the annual salt export reaches 27 million ton. In 1995, the salt export was higher than the import, and Egypt's agricultural lands were desalinizing. Part of this could be due to the large number of subsurface drainage projects executed in the last decades to control the [[water table]] and [[soil salinity]]. | The salt concentration of the water in the Aswan reservoir is about 0.25 kg/m<sup>3</sup>. This is very "sweet" water. At an annual inflow of 55 billion m<sup>3</sup>, the annual salt import reaches 14 million ton. The average salt concentration of the drainage water evacuated into the sea and the coastal lakes is 2.7 kg/m<sup>3</sup> (Egyptian Drainage Research Institute, yearbook 1995/1996). At an annual discharge of 10 billion m<sup>3</sup> (not counting the 2 billion m<sup>3</sup> of salt intrusion from the sea and the lakes, see figure "Water balances"), the annual salt export reaches 27 million ton. In 1995, the salt export was higher than the import, and Egypt's agricultural lands were desalinizing. Part of this could be due to the large number of subsurface drainage projects executed in the last decades to control the [[water table]] and [[soil salinity]]. | ||
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| + | ==History== | ||
| + | [[Image:High Dam Burg Closeup, Aswan, Egypt, Oct 2004.jpg|thumb|left|A closeup view of the Soviet-Egyptian friendship monument]] | ||
| + | The British began construction of the first dam in 1899. Construction lasted until 1902. It was opened in [[December 10]], [[1902]]. The project was designed by Sir [[William Willcocks]] and involved several eminent engineers including Sir [[Benjamin Baker]] and Sir glodstein Mcnabb[[John Aird (engineer)|John Aird]], whose firm, John Aird & Company, was the main contractor. A gravity dam, it was 1,900 m long and 54 m high. The initial design was soon found to be inadequate and the height of the dam was raised in two phases, 1907–1912 and 1929–1933. | ||
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| + | When the dam almost overflowed in 1946 it was decided that rather than raise the dam a third time, a second dam would be built 6 km upriver (about 4 miles). Proper planning began in 1952, just after the [[Egyptian Revolution of 1952|Egyptian Revolution]] led by the Free Officers, of whom [[Gamal Abdel Nasser|Nasser]] was to become leader. At first the USA and Britain were to help finance construction with a loan of [[USD]] $270 million in return for Nasser's leadership on resolving the Arab-Israeli Conflict. However both nations cancelled the offer in July 1956 as part of the secret US-led [[OMEGA Memorandum|'OMEGA' policy]] to marginalize Nasser. A secret Egyptian arms agreement with [[Czechoslovakia]] ([[Eastern Bloc]]) and Egyptian recognition of the [[People's Republic of China]] are cited as possible reasons. | ||
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| + | The Soviet Union stepped in in 1958 and funded the dam project as part of the struggle for influence in Africa during the [[Cold War]], and possibly a third of the cost of the dam was paid for as a long term investment in the region. The Soviets also provided technicians and heavy machinery. The enormous rock and clay dam was designed by the Russian Zuk [[Hydroproject Institute]]. | ||
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| + | {{wide image|Aswan dam.jpg|1024px|A panorama of Aswan Dam}} | ||
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| + | [[Image:Egypt.Aswan.AswanLowDam.01.jpg|right|250px|thumb|Aswan Low Dam]] | ||
| + | Construction began in 1960. The High Dam, ''as-Sad al-'Aali'', was completed on [[July 21]], [[1970]], with the first stage finished in 1964. The reservoir began filling in 1964 while the dam was still under construction and first reached capacity in 1976. The reservoir raised concerns from archaeologists and a rescue operation was begun in 1960 under [[UNESCO]]. Sites were to be surveyed and excavated and 24 major monuments were moved to safer locations (see [[Abu Simbel]]) or granted to countries that helped with the works (such as the [[Temple of Debod|Debod temple]] in Madrid and the [[Temple of Dendur]] in New York). | ||
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| + | ==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. | ||
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| + | ==Environmental and cultural issues== | ||
| + | [[Image:High Dam Burg, Aswan, Egypt, Oct 2004.jpg|225px|thumb|A view from the vantage point in the middle of High Dam towards the "Lotus Flower" tower by the sculptor [[Ernst Neizvestny]].]] | ||
| + | [[Image:Aswan High Dam.jpg|thumb|225px|left|Aswan High Dam (NASA satellite photo)]] | ||
| + | [[Image:High Dam Burg Memorial Wall, Aswan, Egypt, Oct 2004.jpg|225px|thumb|A wall commemorating the completion of Aswan High Dam]] | ||
| + | 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. | ||
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| + | 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 [[River delta|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. | ||
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| + | The need to use artificial [[fertilizer]]s 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 [[River delta|delta]]. | ||
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| + | 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. | ||
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| + | 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. | ||
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==Notes== | ==Notes== | ||
Revision as of 16:42, 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.
Due to the absence of appreciable rainfall, Egypt's agriculture depends entirely on irrigation. With irrigation, two crops per year can be produced, except for sugar cane that has a growing period of almost one year. The high dam at Aswan releases on average 55 billion m3 water per year of which some 46 billion m3 are diverted into the irrigation canals. In Nile valley and delta, almost 8 million feddan (1 feddan is about 1 acre or 0.42 ha) benefit from these waters producing on average 1.8 crop per year. The annual crop consumptive use is about 38 billion m3. Hence, the overall irrigation efficiency is 38/46 = 0.82 or 82%.
Compared to the efficiency elswhere in the world this is a high value. The field irrigation efficiencies are much less, but the losses are re-used downstream. This continuous re-use accounts for the high overall efficiency. The equal distribution of irrigation water over the branch canals taking off from the main irrigation canals leaves to be desired.[1]
| Branch canal | Water delivery in m3/feddan* |
|---|---|
| Kafret Nasser | 4700 |
| Beni Magdul | 3500 |
| El Mansuria | 3300 |
| El Hammami upstream | 2800 |
| El Hammami downstream | 1800 |
| El Shimi | 1200 |
* Period 1 March to 31 July. 1 feddan is about 1 acre or 0.42 ha. Data from Egyptian Water Use Management Project (EWUP)
The salt concentration of the water in the Aswan reservoir is about 0.25 kg/m3. This is very "sweet" water. At an annual inflow of 55 billion m3, the annual salt import reaches 14 million ton. The average salt concentration of the drainage water evacuated into the sea and the coastal lakes is 2.7 kg/m3 (Egyptian Drainage Research Institute, yearbook 1995/1996). At an annual discharge of 10 billion m3 (not counting the 2 billion m3 of salt intrusion from the sea and the lakes, see figure "Water balances"), the annual salt export reaches 27 million ton. In 1995, the salt export was higher than the import, and Egypt's agricultural lands were desalinizing. Part of this could be due to the large number of subsurface drainage projects executed in the last decades to control the water table and soil salinity.
History
The British began construction of the first dam in 1899. Construction lasted until 1902. It was opened in December 10, 1902. The project was designed by Sir William Willcocks and involved several eminent engineers including Sir Benjamin Baker and Sir glodstein McnabbJohn Aird, whose firm, John Aird & Company, was the main contractor. A gravity dam, it was 1,900 m long and 54 m high. The initial design was soon found to be inadequate and the height of the dam was raised in two phases, 1907–1912 and 1929–1933.
When the dam almost overflowed in 1946 it was decided that rather than raise the dam a third time, a second dam would be built 6 km upriver (about 4 miles). Proper planning began in 1952, just after the Egyptian Revolution led by the Free Officers, of whom Nasser was to become leader. At first the USA and Britain were to help finance construction with a loan of USD $270 million in return for Nasser's leadership on resolving the Arab-Israeli Conflict. However both nations cancelled the offer in July 1956 as part of the secret US-led 'OMEGA' policy to marginalize Nasser. A secret Egyptian arms agreement with Czechoslovakia (Eastern Bloc) and Egyptian recognition of the People's Republic of China are cited as possible reasons.
The Soviet Union stepped in in 1958 and funded the dam project as part of the struggle for influence in Africa during the Cold War, and possibly a third of the cost of the dam was paid for as a long term investment in the region. The Soviets also provided technicians and heavy machinery. The enormous rock and clay dam was designed by the Russian Zuk Hydroproject Institute.
Construction began in 1960. The High Dam, as-Sad al-'Aali, was completed on July 21, 1970, with the first stage finished in 1964. The reservoir began filling in 1964 while the dam was still under construction and first reached capacity in 1976. The reservoir raised concerns from archaeologists and a rescue operation was begun in 1960 under UNESCO. Sites were to be surveyed and excavated and 24 major monuments were moved to safer locations (see Abu Simbel) or granted to countries that helped with the works (such as the Debod temple in Madrid and the Temple of Dendur in New York).
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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