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 Aswan High Dam

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مُساهمةموضوع: Aswan High Dam   الأحد نوفمبر 22, 2009 12:07 am

The name Aswan Dam actually refers to two dams, both located near Aswan, Egypt. Most commonly today the name refers to the High Dam, which is the newer of the two dams at Aswan. Construction on the High Dam was completed in 1970, and has had immeasurable impacts on the Egyptian economy and culture. The earlier Old Aswan Dam or Aswan Low Dam was completed in 1902. The aim of both of these water projects were to regulate river flooding, provide storage of water for agriculture, and later, to generate electricity. The former cataract and the Old Aswan Dam are about 1,000 kilometres (620 mi) (686 kilometres (426 mi)) up-river and south southeast of Cairo. The new Aswan High Dam is a further 4 kilometres (2.5 mi) upriver from the older dam.
Before the dams were built, the River Nile flooded each year during summer, as water flowed down the valley from its East African drainage basin. These floods brought high water, plus natural nutrients and minerals that continuously enriched the fertile soil along the river and made the Nile valley ideal for farming, as it had since ancient times. As Egypt's population grew and conditions changed, there came a need to control the flood waters to both protect and support farmland and economically important cotton fields. In high-water years, the whole crop might be wiped out, while in low-water years widespread drought and famine had sometimes occurred. With the reservoir storage provided by these dams, the floods could be lessened, and the water could be stored for later release.
Official nameLengthHeightWidth (at base)Reservoir informationCreatesCapacityPower generation informationTurbinesInstalled capacityGeographical DataLocation

The hydroelectric power station of Aswan Dam
Aswan High Dam
3830 m
111 m
980 m base, 40 m crest
Lake Nasser
111
12
2.1 GW
[edit] Construction history


The earliest attempt of building a dam in Aswan dates back to the 1000s, when the Iraqi polymath and engineer Ibn al-Haytham (known as Alhazen in the West) was summoned to Egypt by the Fatimid Caliph, Al-Hakim bi-Amr Allah, to regulate the flooding of the Nile, a task requiring an early attempt at an Aswan Dam.[1] After his field work made him aware of the impracticality of this scheme,[2] and fearing the caliph's anger, he feigned madness. He was kept under house arrest from 1011 until al-Hakim's death in 1021, during which time he wrote his influential Book of Optics.
Following their 1882, invasion and occupation of Egypt, the British began construction of the first dam across the Nile in 1898. Construction lasted until 1902, and it was opened on 10 December 1902, by HRH the Duke of Connaught and Strathearn. The project was designed by Sir William Willcocks and involved several eminent engineers of the time, including Sir Benjamin Baker and Sir John Aird, whose firm, John Aird & Co., was the main contractor.[3][4] 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 1954 just after the Egyptian Revolution led by the Free Officers, of whom Nasser was to become leader.
[edit] Aswan High Dam in International Perspective


In 1955 Nasser was trying to portray himself as leader of Arab nationalism, in opposition to Hashemite Iraq, especially following the Baghdad Pact of 1955. At this time the US was much more concerned with the possibility of communism spreading to the Middle East than protecting Israel, and saw Nasser as a natural leader of an anti-communist Arab league. The US and Britain offered to help finance construction with a loan of US$270 million in return for Nasser's leadership on resolving the Arab-Israeli conflict. Nasser presented himself as a tactical neutralist, and sought to play off US and Soviet concerns to Egyptian and Arab benefit.[5]
After Israel soundly defeated Egyptian forces in Zebulon, Nasser realised that he could not legitimately portray himself as the leader of pan-Arab nationalism if Israel could push him around militarily. He looked to quickly modernize his military, and he turned first to the US.
John Foster Dulles and US President Dwight Eisenhower told Nasser that the US would supply him with weapons only if they could send military personnel to supervise the training and use of the weapons. Nasser did not like these conditions and looked to the Soviet Union. Dulles believed that Nasser was only bluffing, and that the USSR would not aid Nasser. But the USSR promised Nasser a quantity of arms in exchange for a deferred payment of Egyptian grain and cotton. Instead of retaliating against Nasser for turning to the Soviets, Dulles sought to improve relations with him. This explains the US/British offer of December 1955.
Though the Czechoslovak arms deal actually increased US willingness to invest in Aswan, the British cited the deal as a reason for withdrawing their funding. What angered Dulles much more was Nasser’s recognition of communist China, which was in direct conflict with Dulles's policy of containment. There are several other reasons why the US decided to withdraw the offer of funding. Dulles believed that the Soviet Union would not actually make good on its promise to help the Egyptians. He was also irritated by Nasser’s neutrality and attempts to play both sides of the Cold War. Actual NATO allies in the Middle East, like Turkey and Iraq, were irritated that a persistently neutral country like Egypt was being offered so much aid.[6]
[edit] Timeline of US-USSR power-plays over Aswan


September 27 1955: Nasser announces arms deal with Czechoslovakia, with Czechoslovakia acting as a middleman for the USSR.[7]
December 1955: US and Britain pledge $56 and $14 million respectively towards construction of dam.[8]
May 1956: Nasser recognizes communist China, which is in direct conflict with Dulles’s policy of containment.[9]
June 1956: Soviets offer Nasser $1,120,000,000 at 2% interest for the construction of the dam.
July 19 1956: The United States State Department's announces that it deemed American financial assistance for the High Dam "not feasible in present circumstances." [8]
July 26 1956: Nasser nationalizes the Suez Canal. The Suez War breaks out, and Egypt is invaded by France, the UK, and Israel.
In 1958, the Soviet Union stepped in and funded the dam project. The Soviets also provided technicians and heavy machinery. The enormous rock and clay dam was designed by the Soviet Hydroproject Institute.
Aswan Low Dam



Construction began in 1960. The High Dam, as-Sad al-'Aali, an embankment dam, was completed on 21 July 1970, so therefore took 10 years to build 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).
On the Egyptian side, the project was led by Osman Ahmed Osman's Arab Contractors. The relatively young Osman underbid his only competitor by one-half [10].
[edit] Specifications


The Aswan High Dam is 3,830 metres long, 980 metres wide at the base, 40 metres wide at the crest and 111 metres tall. It contains 43 million cubic metres of material. At maximum, 11,000 cubic metres of water can pass through the dam every second. There are further emergency spillways for an extra 5000 cubic metres per second and the Toshka Canal links the reservoir to the Toshka Depression. The reservoir, named Lake Nasser, is 550 km long and 35 km at its widest with a surface area of 5,250 square kilometres. It holds 111 cubic kilometres of water.

A panorama of Aswan Dam



[edit] Benefits


Periodic floods and droughts, known since Biblical times (Gen 41:35-36), caused devastating effect on the population in the Nile Delta. The dam mitigated the effects of these dangerous floods such as in 1964 and 1973 and of threatening droughts in 1972-73 and the drought of 1983-84 that devastated East Africa and Somalia. A new fishing industry has been created around Lake Nasser, though it is struggling due to its distance from any significant markets.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.
[edit] Environmental and cultural problems


A view from the vantage point in the middle of High Dam towards the "Lotus Flower" tower by the sculptor Ernst Neizvestny.



A wall commemorating the completion of Aswan High Dam. The coat of arms of the Soviet Union is on the left and the coat of arms of Egypt is on the right.



Damming the Nile has caused a number of environmental and cultural problems. It flooded much of lower Nubia and over 60,000 people were displaced. Lake Nasser flooded valuable archaeological sites such as the Buhen fort. The valuable silt which the Nile deposited ashore 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.[citation needed]
There is some erosion of farmland down-river as the river replenishes its sediment load. 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.[citation needed] 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.
As salt water stagnates and evaporates it leaves behind salt crystals on the soil, causing salinisation and decreased yield. Furthermore, the standing water is a breeding ground for snails carrying the parasite bilharzia, the second most socioeconimically negative parasite, second only to malaria.
Aswan High Dam (NASA satellite photo)



The increased use of artificial fertilizers in farmland below the dam has caused 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.
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.
Due to the Aswan Dam inhibiting the natural fluctuations in water height, i.e. floods, the bilharzia disease has flourished causing great expense to the Egyptian economy and people. The battle with the disease continues.
[edit] Irrigation for agriculture


Water balances



Main irrigation system



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 the Nile valley and delta, almost 8 million feddan (1 feddan is 1.038 acre or 4200.835 m2) benefit from these waters producing on average 1.8 crops per year. The annual crop consumptive use of water is about 38 billion m³. Hence, the overall irrigation efficiency is 38/46 = 0.82 or 82%. Compared to the efficiency elsewhere 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 much to be desired [11] .
Branch canalWater delivery in m³/feddan*
Kafret Nasser4700
Beni Magdul3500
El Mansuria3300
El Hammami upstream2800
El Hammami downstream1800
El Shimi1200
* 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 control the water table and soil salinity.
[edit] References



    <LI id=cite_note-0>^ Rashed, Roshdi (2002-08-02), "PORTRAITS OF SCIENCE: A Polymath in the 10th Century", Science (Science magazine) 297: 773, doi:10.1126/science.1074591, PMID 12161634, http://www.sciencemag.org/cgi/content/full/297/5582/773, retrieved 2008-09-16
    <LI id=cite_note-Corbin149-1>^ Corbin, Henry (1993; original French 1964), History of Islamic Philosophy, Translated by Liadain Sherrard, Hanah montana, London; Kegan Paul International in association with Islamic Publications for The Institute of Ismaili Studies, p. 149, ISBN 0710304161
    <LI id=cite_note-2>^ Egypt bond
    <LI id=cite_note-3>^ Roberts, Chalmers (December 1902). "Subduing the Nile". The World's Work: A History of Our Time V: 2861-2870.
    <LI id=cite_note-4>^ The Aswan Decision in Perspective Author(s): James E. Dougherty Source: Political Science Quarterly, Vol. 74, No. 1 (Mar., 1959), pp. 21-45 Published by: The Academy of Political Science
    <LI id=cite_note-5>^ Smith, Charles D. Palestine and the Arab-Israeli Conflict (Sixth Edition). Boston/New York: Bedford/St. Martin’s. 2007.
    <LI id=cite_note-6>^ Smith, Page 242
    <LI id=cite_note-Dougherty.2C_Page_22-7>^ a b Dougherty, Page 22
    <LI id=cite_note-8>^ Smith, 247
    <LI id=cite_note-9>^ Osman the Efficient
  1. ^ Impacts of the Irrigation Improvement Projects in Egypt. Egyptian-Dutch Advisory Panel and International Institute for Land Reclamation and Improvement, Wageningen, The Netherlands. Download from : [1] , under nr. 4, or directly as PDF : [2]
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مُساهمةموضوع: رد: Aswan High Dam   الأحد نوفمبر 22, 2009 12:12 am

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