Асуан тоғаны: тарихы мен маңызы

the older Aswan Dam built downstream in 1902

The Aswan Dam, or more specifically since the 1980s, the Aswan High Dam, is one of the world's largest embankment dams, which was built across the Nile in Aswan, Egypt, between 1960 and 1970. When it was completed, it was the tallest earthen dam in the world, eclipsing the United States' Chatuge Dam. Its significance largely upstaged the previous Aswan Low Dam initially completed in 1902 downstream. Based on the success of the Low Dam, then at its maximum utilization, construction of the High Dam became a key objective of the new regime the Free Officers movement of 1952; with its ability to better control flooding, provide increased water storage for irrigation and generate hydroelectricity, the dam was seen as pivotal to Egypt's planned industrialization. Like the earlier implementation, the High Dam has had a significant effect on the economy and culture of Egypt. Before the High Dam was built, even with the old dam in place, the annual flooding of the Nile during late summer had continued to pass largely unimpeded down the valley from its East African drainage basin. These floods brought high water with natural nutrients and minerals that annually enriched the fertile soil along its floodplain and delta; this predictability had made the Nile valley ideal for farming since ancient times. However, this natural flooding varied, since high water years could destroy the whole crop, while low water years could create widespread drought and consequently famine. Both these events had continued to occur periodically. As Egypt's population grew and technology increased, both a desire and the ability developed to completely control the flooding, and thus both protect and support farmland and its economically important cotton crop. With the greatly increased reservoir storage provided by the High Aswan Dam, the floods could be controlled and the water could be stored for later release over multiple years. The Aswan Dam was designed by Nikolai Aleksandrovich Malyshev of the Moscow based Hydroproject Institute.

The earliest recorded attempt to build a dam near Aswan was in the 11th century, when the Arab 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. His field work convinced him of the impracticality of this scheme.

The British began construction of the first dam across the Nile in 1898. Construction lasted until 1902 and the dam was opened on 10 December 1902. The project was designed by Sir William Willcocks and involved several eminent engineers, including Sir Benjamin Baker and Sir John Aird, whose firm, John Aird & Co., was the main contractor.

In 1952, the Greek Egyptian engineer Adrian Daninos began to develop the plan of the new Aswan Dam. Although the Low Dam was almost overtopped in 1946, the government of King Farouk showed no interest in Daninos's plans. Instead the Nile Valley Plan by the British hydrologist Harold Edwin Hurst was favored, which proposed to store water in Sudan and Ethiopia, where evaporation is much lower. The Egyptian position changed completely after the overthrow of the monarchy, led by the Free Officers Movement including Gamal Abdel Nasser. The Free Officers were convinced that the Nile Waters had to be stored in Egypt for political reasons, and within two months, the plan of Daninos was accepted. Initially, both the United States and the USSR were interested in helping development of the dam. Complications ensued due to their rivalry during the Cold War, as well as growing intra Arab tensions. In 1955, Nasser was claiming to be the leader of Arab nationalism, in opposition to the traditional monarchies, especially the Hashemite Kingdom of Iraq following its signing of the 1955 Baghdad Pact. At that time the U. S. feared that communism would spread to the Middle East, and it saw Nasser as a natural leader of an anticommunist procapitalist Arab League. America and the United Kingdom offered to help finance construction of the High Dam, with a loan of $270 million, in return for Nasser's leadership in resolving the Arab Israeli conflict. While opposed to communism, capitalism, and imperialism, Nasser identified as a tactical neutralist, and sought to work with both the U. S. and the USSR for Egyptian and Arab benefit. After the UN criticized a raid by Israel against Egyptian forces in Gaza in 1955, Nasser realized that he could not portray himself as the leader of pan Arab nationalism if he could not defend his country militarily against Israel. In addition to his development plans, he looked to quickly modernize his military, and he turned first to the U. S. for aid. American Secretary of State John Foster Dulles and President Dwight Eisenhower told Nasser that the U. S. would supply him with weapons only if they were used for defensive purposes and if he accepted American military personnel for supervision and training. Nasser did not accept these conditions, and consulted the USSR for support. Although Dulles believed that Nasser was only bluffing and that the USSR would not aid Nasser, he was wrong: the USSR promised Nasser a quantity of arms in exchange for a deferred payment of Egyptian grain and cotton. On 27 September 1955, Nasser announced an arms deal, with Czechoslovakia acting as a middleman for the Soviet support. Instead of attacking Nasser for turning to the Soviets, Dulles sought to improve relations with him. In December 1955, the US and the UK pledged $56 and $14 million, respectively, toward construction of the High Aswan Dam. Though the Czech arms deal created an incentive for the US to invest at Aswan, the UK cited the deal as a reason for repealing its promise of dam funds. Dulles was angered more by Nasser's diplomatic recognition of China, which was in direct conflict with Dulles's policy of containment of communism. Several other factors contributed to the US deciding to withdraw its offer of funding for the dam. Dulles believed that the USSR would not fulfill its commitment of military aid. He was also irritated by Nasser's neutrality and attempts to play both sides of the Cold War. At the time, other Western allies in the Middle East, including Turkey and Iraq, were resentful that Egypt, a persistently neutral country, was being offered so much aid. In June 1956, the Soviets offered Nasser $1.12 billion at 2% interest for the construction of the dam. On 19 July the U. S. State Department announced that American financial assistance for the High Dam was "not feasible in present circumstances." On 26 July 1956, with wide Egyptian acclaim, Nasser announced the nationalization of the Suez Canal that included fair compensation for the former owners. Nasser planned on the revenues generated by the canal to help fund construction of the High Dam. When the Suez War broke out, the United Kingdom, France, and Israel seized the canal and the Sinai. But pressure from the U. S. and the USSR at the United Nations and elsewhere forced them to withdraw. In 1958, the USSR proceeded to provide support for the High Dam project. In the 1950s, archaeologists began raising concerns that several major historical sites, including the famous temple of Abu Simbel were about to be submerged by waters collected behind the dam. A rescue operation began in 1960 under UNESCO (for details see below under Effects). Despite its size, the Aswan project has not materially hurt the Egyptian balance of payments. The three Soviet credits covered virtually all of the project's foreign exchange requirements, including the cost of technical services, imported power generating and transmission equipment and some imported equipment for land reclamation. Egypt was not seriously burdened by payments on the credits, most of which were extended for 12 years with interest at the very low rate of 2 1/2%. Repayments to the USSR constituted only a small net drain during the first half of the 1960s, and increased export earnings derived from crops grown on newly reclaimed land have largely offset the modest debt service payments in recent years. During 1965–70, these export earnings amounted to an estimated $126 million, compared with debt service payments of $113 million.

The Aswan High Dam is long, wide at the base, wide at the crest and tall. It contains of material. At maximum, of water can pass through the dam. There are further emergency spillways for an extra , and the Toshka Canal links the reservoir to the Toshka Depression. The reservoir, named Lake Nasser, is long and at its widest, with a surface area of It holds of water.

The High Dam has resulted in protection from floods and droughts, an increase in agricultural production and employment, electricity production, and improved navigation that also benefits tourism. Conversely, the dam flooded a large area, causing the relocation of over 100,000 people. Many archaeological sites were submerged while others were relocated. The dam is blamed for coastline erosion, soil salinity, and health problems. The assessment of the costs and benefits of the dam remains controversial decades after its completion. According to one estimate, the annual economic benefit of the High Dam immediately after its completion was , $587 million using the exchange rate in 1970 of $2.30 per ): from agricultural production, from hydroelectric generation, from flood protection, and from improved navigation. At the time of its construction, total cost, including unspecified "subsidiary projects" and the extension of electric power lines, amounted to Not taking into account the negative environmental and social effects of the dam, its costs are thus estimated to have been recovered within only two years. One observer notes: "The impacts of the Aswan High Dam ( ) have been overwhelmingly positive. Although the Dam has contributed to some environmental problems, these have proved to be significantly less severe than was generally expected, or currently believed by many people." Another observer disagreed and he recommended that the dam should be torn down. Tearing it down would cost only a fraction of the funds required for "continually combating the dam's consequential damage" and of fertile land could be reclaimed from the layers of mud on the bed of the drained reservoir. Samuel C. Florman wrote about the dam: "As a structure it is a success. But in its effect on the ecology of the Nile Basin – most of which could have been predicted – it is a failure". Periodic floods and droughts have affected Egypt since ancient times. The dam mitigated the effects of floods, such as those in 1964, 1973, and 1988. Navigation along the river has been improved, both upstream and downstream of the dam. Sailing along the Nile is a favorite tourism activity, which is mainly done during the winter when the natural flow of the Nile would have been too low to allow navigation of cruise ships. A new fishing industry has been created around Lake Nasser, though it is struggling due to its distance from any significant markets. The annual production was about 35 000 tons in the mid 1990s. Factories for the fishing industry and packaging have been set up near the Lake. Other estimates put evaporation from Lake Nasser at between 10 and 16 cubic km per year.

The dam powers twelve generators each rated at , with a total of Power generation began in 1967. When the High Dam first reached peak output in 1970, it produced around half of Egypt's production of electric power (about 15 percent by 1998), and it gave most Egyptian villages the use of electricity for the first time. The High Dam has also improved the efficiency and the extension of the Old Aswan Hydropower stations by regulating upstream flows. By 1971 estimation, power output at Aswan won't reach much more than half of the plant's theoretical capacity, because of limited water supplies and the differing seasonal water use patterns for irrigation and power production. Agricultural demand for water in the summer far exceeds the amount needed to meet the comparatively low summer demand for electric power. Heavy summer irrigation use, however, will leave insufficient water under Egyptian control to permit hydroelectric power production at full capacity in the winter. Technical studies indicate that a maximum annual output of 5 billion kWh appears to be all that can be sustained due to fluctuations in Nile flows.

Lake Nasser flooded much of lower Nubia and 100,000 to 120,000 people were resettled in Sudan and Egypt. In Sudan, 50,000 to 70,000 Sudanese Nubians were moved from the old town of Wadi Halfa and its surrounding villages. Some were moved to a newly created settlement on the shore of Lake Nasser called New Wadi Halfa, and some were resettled approximately south to the semi arid Butana plain near the town of Khashm el Girba up the Atbara River. The climate there had a regular rainy season as opposed to their previous desert habitat in which virtually no rain fell. The government developed an irrigation project, called the New Halfa Agricultural Development Scheme to grow cotton, grains, sugar cane and other crops. The Nubians were resettled in twenty five planned villages that included schools, medical facilities, and other services, including piped water and some electrification. In Egypt, the majority of the 50,000 Nubians were moved three to ten kilometers from the Nile near Edna and Kom Ombo, downstream from Aswan in what was called "New Nubia". Housing and facilities were built for 47 village units whose relationship to each other approximated that in Old Nubia. Irrigated land was provided to grow mainly sugar cane. In 2019–20, Egypt started to compensate the Nubians who lost their homes following the dam impoundment.

Before the construction of the High Dam, the Nile deposited sediments of various particle size – consisting of fine sand, silt and clay – on fields in Upper Egypt through its annual flood, contributing to soil fertility. However, the nutrient value of the sediment has often been overestimated. 88 percent of the sediment was carried to the sea before the construction of the High Dam. The nutrient value added to the land by the sediment was only 6,000 tons of potash, 7,000 tons of phosphorus pentoxide and 17,000 tons of nitrogen. These amounts are insignificant compared to what is needed to reach the yields achieved today in Egypt's irrigation. Also, the annual spread of sediment due to the Nile floods occurred along the banks of the Nile. Areas far from the river which never received the Nile floods before are now being irrigated. A more serious issue of trapping of sediment by the dam is that it has increased coastline erosion surrounding the Nile Delta. There is a lack of reliable statistics.

Before the construction of the High Dam, groundwater levels in the Nile Valley fluctuated per year with the water level of the Nile. During summer when evaporation was highest, the groundwater level was too deep to allow salts dissolved in the water to be pulled to the surface through capillary action. With the disappearance of the annual flood and heavy year round irrigation, groundwater levels remained high with little fluctuation leading to waterlogging. Soil salinity also increased because the distance between the surface and the groundwater table was small enough (1–2 m depending on soil conditions and temperature) to allow water to be pulled up by evaporation so that the relatively small concentrations of salt in the groundwater accumulated on the soil surface over the years. Since most of the farmland did not have proper subsurface drainage to lower the groundwater table, salinization gradually affected crop yields. Drainage through sub surface drains and drainage channels is essential to prevent a deterioration of crop yields from soil salinization and waterlogging. By 2003, more than 2 million hectares have been equipped with a subsurface drainage system at a cost from 1973 to 2002 of about $3.1 billion.

Contrary to many predictions made prior to the Aswan High Dam construction and publications that followed, that the prevalence of schistosomiasis (bilharzia) would increase, it did not. This assumption did not take into account the extent of perennial irrigation that was already present throughout Egypt decades before the high dam closure. By the 1950s only a small proportion of Upper Egypt had not been converted from basin (low transmission) to perennial (high transmission) irrigation. Expansion of perennial irrigation systems in Egypt did not depend on the high dam. In fact, within 15 years of the high dam closure there was solid evidence that bilharzia was declining in Upper Egypt. S. haematobium has since disappeared altogether. Suggested reasons for this include improvements in irrigation practice. In the Nile Delta, schistosomiasis had been highly endemic, with prevalence in the villages 50% or higher for almost a century before. This was a consequence of the conversion of the Delta to perennial irrigation to grow long staple cotton by the British. This has changed. Large scale treatment programmes in the 1990s using single dose oral medication contributed greatly to reducing the prevalence and severity of S. mansoni in the Delta.

Sediment deposited in the reservoir is lowering the water storage capacity of Lake Nasser. The reservoir storage capacity is 162 km3, including 31 km3 dead storage at the bottom of the lake below above sea level, 90 km3 live storage, and 41 km3 of storage for high flood waters above above sea level. The annual sediment load of the Nile is about 134 million tons. This means that the dead storage volume would be filled up after 300–500 years if the sediment accumulated at the same rate throughout the area of the lake. Obviously sediment accumulates much faster at the upper reaches of the lake, where sedimentation has already affected the live storage zone. A concern before the construction of the High Dam had been the potential drop in river bed level downstream of the Dam as the result of erosion caused by the flow of sediment free water. Estimates by various national and international experts put this drop at between and However, the actual drop has been measured at , much less than expected. According to one source, bricks are now being made from new techniques which use a sand clay mixture and it has been argued that the mud based brick industry would have suffered even if the dam had not been built.