Science Fair Project Encyclopedia
Normally, the River Nile floods in the summer every year as waters from Ethiopia flow down the river. These floods brought nutrients and mineral that made the soil around the Nile fertile and ideal for farming. As the population along the river grew there came the need to control the flood waters to protect farmland and cotton fields. In a high-water year, the whole crop may be entirely wiped out, while in a low-water year there was widespread drought and famine.
The British began construction of the first dam in 1899 and it was completed in 1902. 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 up-river. Proper planning began in 1952, just after the Nasser revolution, and at first the US was to help finance construction with a loan of USD $270 million. The aid offer was withdrawn in mid-1956 when Egypt formally recognised the People's Republic of China. The Egyptian government intended to continue the project alone and use the revenues of the Suez Canal to help pay for construction. But in the Cold War struggle for influence in Africa the Soviet Union stepped in 1958 and possibly a third of the cost of the dam was paid for as a gift. They 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, El Saad 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 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).
The Aswan High Dam is 3,600 m in length, 980 m wide at the base, 40 m wide at the crest and 111 m tall. It contains 43 million m³ of material. At maximum, 11,000 m³ of water can pass through the dam every second. There are further emergency spillways for an extra 5000 m³ per second and the Toshka canal links the reservoir to the Toshka depression. The reservoir, named Lake Nasser, is 480 km long and 16 km at its widest with a surface area of 6,000 km² and holds 150 to 165 km³. It flooded much of lower Nubia and over 90,000 people were displaced. With hydroelectric output of 2.1 gigawatts, the dam holds twelve generators each rated at 175 megawatts. 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 electricity for the first time. The effects of dangerous floods in 1964 and 1973 and of threatening droughts in 1972–73 and 1983–84 were mitigated. A new fishing industry has been created around Lake Nasser, though it is struggling due to its distance from any significant markets.
In addition to the benefits, however, damming the Nile caused a number of environmental issues. The silt which made the Nile region fertile is instead held at the dam, leading to (expected) silting of the reservoir, which will eventually (an estimated 500 years) render Lake Nasser useless for water storage volume.
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 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 further into the delta. Mediterranean fish stocks are also impacted 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, but appear to be recovering. 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 construction of the dam also had a major political effect. Lake Nasser is huge, and almost all of Egypt's population lives in the Nile valley. This means that if the dam were to be destroyed, the resulting flood would effectively destroy Egypt completely. It has been rumoured that during the Yom Kippur War the dam – heavily defended by flak – was paint-bombed by Israeli Air Force aircraft, and it has been further suggested that this was a major factor in Anwar Sadat's decision to make peace with Israel at Camp David.
- Sayed El-Sayed and Gert L. van Dijken 'The southeastern Mediterranean ecosystem revisited: Thirty years after the construction of the Aswan High Dam.'
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