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Technical and ecological impacts of the High Aswan Dam
Journal ofttydrology, 53 (1981) 73--84
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Elsevier Scientific Publishing Company, Am:;terdam -- Printed in The Netherlands
[1]
TECHNICAL A N D ECOLOGICAL IMPACTS OF THE HIGH ASWAN DAM
ABDEL-AZIZ I. KASHEF*
Department of Civil Engineering, Yarmouk University, Irbid (Jordan) (Received July 30, 1980; accepted for publication October 8, 1980)
ABSTRACT Kashef, A.I., 1981. Technical and ecological impacts of the High Aswan Dam. J. Hydrol., 53: 73--84. Since the High Aswan Dam was planned in 1952 until it was completed in 1970, it was associated with numerous technical, social and political problems. The side-effects of the dam after its construction until the present time are the concern of various authorities all over the world. The technical and ecological impacts of the dam are discussed and the potential remedies are presented. A channel is proposed from the reservoir downstrean the dam with a branch to feed the Western Desert areas. The performance of the channel could be improved by a proposed submerged weir to divert the silts back to Egypt. The proposed remedy would bring back the fertility of the land, reduce the cost of chemical fertilizers, prevent erosion in the Nile and other waterways, stop the advance of the Mediterranean shoreline and would solve other social, technical and economic problems.
INTRODUCTION
The High Aswan Dam was one of a series of dams on the Nile that were constructed to improve the water-resources management since the nineteenth century. The first of these dams was known as the Qanater E1Khairia Barrage. This barrage consists of a set o f five barrages, ~ 25 km north of Cairo, and was used mainly as a diversion dam in order to feed high-level canals. Its operations started in 1886 for the main purpose of changing the basin irrigation system to a perennial system which allowed raising more than one crop a year, including cotton (Kashef, 1981). It is now serving as a touristic structure after the present Delta Barrage was built in the 1930's. In 1894, Sir William Willcocks (1904) proposed a storage dam at Aswan, a city located in a rainless region ~ 3 6 0 km north of Wadi Halfa (which is the m o s t remote town at the southern border of Egypt). The Aswan Dam was constructed between 1898 and 1902 with a storage capacity of 1 km 3 . It was heightened twice, in 1912 and 1934, to reach a maximum storage capacity of 5.3 km 3 .
* Formerly with the High Aswan Dam Authority, Cairo, Egypt, 1952--1954.
0022-1694/81/0000--0000/$02.50
© 1981 Elsevier Scientific Publishing Company
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These two dams prompted the construction of an excellent net of irrigation and drainage canals. They were followed by other dams and barrages: (a) the Naga Hamadi, Esna, Assiut, Zifta and Edfina barrages in Egypt; (b) the Gebel Aulia and Sennar dams in Sudan; and (c) the Owen Falls Dam in Uganda. All these dams, with the exception of Owen Falls and the High Aswan dams, were designed on the basis of annual storage (Kashef, 1981). Water is stored yearly from the excess of the annual flood flow during the period August-January in order to use it during the subsequent period of low water supply from February to July. Shortly after the flood peak, the storage begins to minimize silt accumulation. In order to meet the ultimate water demands necessary for raising more crops in Egypt (the population increased from 2.5 million in 1840 to 40 million in 1979) and Sudan, additional water projects were suggested and some of the old barrages were strengthened. Some of the suggested dams had to be built outside Egypt. In order to avoid political implications, Adrian Daninos suggested a high dam a t Aswan with a huge capacity within the Egyptian territory. The idea was not at first appealling to the officials because of the prohibitive costs and also due to the lack of worldwide experience in dams of such capacity (164 km s ) which had to be built on a sand deposit 2 0 0 m thick rather than bedrock. Finally, the project reached the drawing board in 1952 after it had been recommended by the then newly established "National Production Council". The dam was constructed to provide long-term storage to meet the demands of agricultural expansion, to generate electricity, to guarantee water supply during the unexpectedly low-stage years and to protect the land from high floods. The optimistic program of agricultural land expansion in Egypt calls for irrigating an additional area of 1.5" 106 feddans*. The agricultural land in Egypt is limited within the Nile valley and few scattered desert areas. Thus the land expansion is limited to the desert areas alongthe valley borders and other unreclaimed areas in the delta that need excessive waters to make them productive. Other hopes included the diversion of the Nile water to the desert area beyofld the boundaries of the valley such as the series of oases in the Western Desert (known presently as the "New Valley Project"), the Sinai peninsula, and the Mediterranean coastal strip west of Alexandria.
H Y D R O L O G I C A L AND S T R U C T U R A L C O N S I D E R A T I O N S
The hydrological planning of a long-term (or hold-over or century) storage dam is by no means a routine matter. The reservoir capacity was estimated on the basis of an average flow over a number og selected consecutive years. This average should meet the water requirements downstream the dam. Although Nile records are available since the seventh century (Jarvis, 1936), A f e d d a n is an old E g y p t i a n land m e a s u r e m e n t ; 1 f e d d a n = 1.038 acre = 4 2 0 0 . 8 m : .
75 the average annual flows at Aswan (or Wadi Halfa) are irregular and unpredictable (Kashef, 1981). The design of the High Aswan Dam was based on an average of 84 km 3/yr. which was also used as the basis of the 1959 International Water Agreement between Egypt and Sudan. However, the actual average over a period of 30 years (1870--1899) was 109 km 3/yr. and that over the following fifty years (1900--1949) was 83 km 3/yr. Over a period of 95 years (1871--1965), the lowest average was 45.5 km 3/yr. in 1913 and the highest was 137.0 km 3/yr. in 1878 (Clawson et al., 1971). The water available for storage in a certain year would be the amount of flow in excess of the net average value which is computed from the selected gross average (84 km 3/yr.) reduced by the seepage and evaporation losses and also by the amount of water allocated to Sudan (a maximum of 15.5 km 3/yr. measured at Aswan according to the 1959 agreement). The loss in the reservoir was estimated as 11.0 km a/yr. (I.B.C., 1955). If in one year the flow is less than the selected average, water should be released from the reservoir to supplement the natural flow. If this happens frequently before the dam is full it would tremendously disrupt the planned water-management schedules. The planned maximum reservoir capacity of the High Aswan Dam is 164 km 3 when the water level reaches 1 S 2 m a.s.1. (or 9 7 m above river bed). However, after construction of tho dam, the actual losses were apparently greater than those estimated previously and the highest capacity of 115.0 km 3 was reached in October 1975 {Table I) at an elevation of 1 7 5 . 0 0 m (Waterbury, 1979}. Also many reports discarded the original design capa~:ity of 1 6 4 k m 3 and claimed that the maximum capacity should not exceed 1 5 7 . 4 k m a which as yet has never been attained (Waterbury, 1979). A breakdown of the revised maximum capacity of 157 km 3 is given in Table II. The reservoir of the dam is known as Lake Nasser in Egypt (Fig. 1) and as Lake Nubia for its southern portion located within the Sudanese territory. Its shortest length along the center line is 350 km in Egypt and 150 km in Sudan (Raheja, 1973). However, the total lengths of its shorelines are 8803 and 5960 km at elevations of 180 and 160 m, respectively. The length of the eastern shoreline is almost two times that of the western shoreline. At an elevation of 180 m, the maximum and mean depths are respectively 81 and 25 m; and the maximum and mean widths are respectively 25 and 17.95 km (Raheja, 1973). The lake has many khors or lagoons (arms), some of which reach more than 50 km in length. There axe 48 khors on the eastern side totalling 576 km in length and 37 on the western side with a total length of 394 km. The body of the dam itself lies on a deposit of 200 m thick sand underlain by granitic bedrock. It consists of a main rockfill dam connected with two cofferdams of smaller sizes, one upstream and one downstream. Between the river banks the length is 3600 m at the top and 5 2 0 m at the bottom. The widths of the dam axe 980 m at the bottom and 40 m at the top and its height
127.60 132.70 142.45 151.25 156.55 161.30 164.88
175.00 182.00
1964--1965 1965--1966 1966--1967 1967--1968 1968--1969 1969--1970 1970--1971
Total Average Oct. 1 9 7 5 Never a t t a i n e d
582.901 83.27 ---
119.430 79.550 69.120 92.370 71.102 69.539 81.790
Inflow* 1 (km 3 )
547.003 78.143 ---
119.082 78.497 67.760 87.290 62.740 61.263 70.371
O u t f l o w and accumulation -*1 in reservoir (km 3 )
S o u r c e s : ,1 Wafa and L a b i b ( 1 9 7 3 ) ; , 2 W a t e r b u r y ( 1 9 7 9 ) .
Maximum reservoir height* 1 (m)
Period
D a t a o n s t o r a g e and losses for t h e High A s w a n ' D a m , E g y p t
TABLE I
35.896 5.128
0.348 1.053 1.360 5.080 8.362 8.276 11.417
Actual reservoir losses* 1 (km 3 )
13.9 15.3--16.7
9.4 78.5 3,500
115.0 157.4
5.9 41.1 2,200
5,168 6,200
1.4
Estimated evaporation losses .2 (km 3 ) 9.8
Reservoir v o l u m e .2 (km 3 )
550
(kin ~ )
surface .2
Reservoir
77 T A B L E II Breakdown of the revised m a x i m u m reservoir capacity ( k m 3 ) of the Aswan D a m (a) Share of Egypt d o w n s t r e a m the d a m (including 30 k m 3 for hydroelectric power) (b) Share of Sudan measured at Aswan or "~20.5 k m 3 in t h e areas of irrigation (Morrice and Allan, 1959); if this is totally used it should be d e d u c t e d ; t o the best of the a u t h o r ' s knowledge, Sudan is using at present ~ 5.5 k m 3 after the construction o f the Roseires and Khashm el Girba dams in Sudan (Kashef, 1981) (c) Evaporation and seepage losses (d) Volume of silt deposits accumulated through hundreds of years (e) Long-term storage for irrigation and flood control
55.5
18.5 11.0 30.0 42.0 Total
157.0
~ Nile
. ~@A Kom Ombo swan Darn
branch t o oases (Western
Desert
Loke N a s s e r"~
A
Ibrirn
Abu 2 /
'
^~,~Tushka
S i m b e l L~" ~ ¢ _ J~a EGYPT
Adinan
SUDAN
f~ Lake Nubia
A - E n Ior'g'ed
Fig. 1. The reservoir of the High Aswan Dam existing of Lake Nasser (Egypt) and Lake Nubia (Sudan}.
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is 111 m above the river bed. The upstream cofferdam is 600 m long and 50 m high, while the downstream cofferdam is 5 0 0 m long and 30 m high. The dam contains a total of 4 3 " 1 0 6 m 3 of materials which would be equivalent to 17 times the volume of Cheop's pyramid or 25 times the volume of the Empire State Building in New York City (Wisely, 1972}. In order to prevent seepage losses beneath the dam a huge grout curtain, 2 0 0 m deep, was constructed. The construction of the dam started on January 9, 1960 and was completed in 1968. The closure of the Nile t o o k place, for the first time, in :/964. The Aswan power station consists of twelve turbo generators able to churn out 0.175"106 kW-hr, each (total 2.1"106 kW-hr.) and fed by tunnels discharging 1.0 km 3/day (Wisely, 1972). The construction of the power station was completed in 1970 on the east side of the river. In the original plans (I.B.C., 1955), diversion channels with tunnel segments were suggested on the western side of the river. Also a horizontal impervious blanket in the upstream was proposed. Both designs were eliminated by the financiers (U.S.S.R.) who also wished to eliminate the grout curtain but were strongly opposed by the Egyptian engineers. Altt~ough it seems that no serious side-effects were developed from the elimination of the horizontal blanket, the elimination of the diversion channels on the western side produced serious problems to the country and its people as explained in the following section.
SIDE-EFFECTS OF THE DAM
:ilting and erosion The annual total sediments passing Wadi Halfa were estimated between 100"106 and 140'106 t (Aleem, 1972). The released sediments from Aswan were estimated at 26.2"106 , 5.5"106 and 3"106 t/yr. during 1964 (closure of the Nile), 1965 and 1966, respectively (Hammad, 1972). All sediments are presently deposited in the southern region of Lake Nasser. The released clear water with its high velocities starts to pick up sediments from the river bed: ~ 1 1 " 1 0 6 and ~6"106 t/yr. during 1965 and 1966, respectively, from Aswan to Cairo; a distance of ~ 9 6 5 km (Hammad, 1972). It was reported that 88% of the sediments were carried to the sea before constructing the High Aswan Dam and ~ 9 % were deposited on the land. Assuming that the specific weights of the deposited silt vary from 1.12 to 1.6 t / m 3 , the annual decrease in water storage would roughly vary between 62.5~106 and 125"106 m 3 . The lower figure (62.5"106 m 3 ) may have been used in designing the capacity of the High Aswan Dam where silt storage was estimated at 30 km 3 in 500 years (I.B.C., 1955). The present lack of silt in Egypt leads to excessive erosion in the river channel and the Nile delta region due to the high velocities of clear water.
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Some research workers believe that the scour action may stabilize in the future (Hammad, 1972). In the author's opinion, this may be true yet after the damage has been done. It has also been reported (Wisely, 1972) that three low-head dams are planned between Aswan and Cairo at a cost of US $100 million to alleviate the degradation process. {This idea was recently discarded.)
Socio-economic impacts Social and economic side-effects of the High Aswan Dam include drastic losses in the fish industry, gradual deterioration of the main summer resorts along the Mediterranean, the spread of diseases and the migration of entire villages which were inundateci by the reservoir of the dam. Before the construction of the dam, the annual fish catch from the Nile, the lakes, the Mediterranean and Red Sea was estimated at 1 2 . 5 - 1 0 4 t (Aleem, 1972). The sardinella catches have dropped because of the lack of silt from 1.5"104 t in 1964 to 0.46°104 t in 1965. It dropped further in 1966 to only 554 t. It is expected, however, to catch 2-104 t annually from Lake Nasser. The extremely hot weather at the site of the dam and the long distance from the main market (Cairo and the Nile delta) would add more problems to lessen the effects of this partial loss recovery. The rapid erosion of the northern summer resorts due to the lack of silts and the high velocities of clear water is threatening the beaches and the recreation industry, especially near Damietta and Rosetta, including the famous resort of Alexandria. Economic losses have already been reached in these areas. The conversion of the basin irrigation system to perennial in southern Egypt led to spreading of the malaria and schistosomiasis (bilharzia) diseases for the first time in these areas. As a mat'~er of fact, the conversion in southern Egypt started at a very slow rate during World War II but it could not be c,ompleted without additional water. In some farms shallow artesian wells were used to supplement the basin irrigation and raise more than one crop a year. Because of the expenses of these wells, the water was used wisely and the diseases were not so widely spread as at the present time where water runs in the canals and flows over the land by gravity (free of charge). A b o u t 106 acre (4047 km 2 ) of land in the Nile Valley were still under basin irrigation in 1950 and their conversion is almost complete (Clawson et al., 1971). The over-use of water by farmers and the resulting diseases are now closely watched by the government. Small pumps and hand-lifting tools (based mainly on the Archimedian screw principle) are used at present in areas where water is intentionally lowered in the irrigation canals (Kashef, 1981). A large-scale drainage project (cost b U S $600 million) has been initiated to lower the high water table which resulted from the gravity irrigation procedure. This would definitely help to confine spreading of diseases.
80 Due to flooding of the land south of Aswan, 100,000 persons from the Nubian region were resettled in Kom Ombo (a plateau 46 km north of Aswan and on the east side of the river) in 16,548 houses scattered over 43 newly constructed villages (Wisely, 1972). Additionally, 500,000 Nubians were resettled in Sudan in 1962 in Khashm el Girba with their 18,000 heads of livestock; twenty villages were constructed with 250 houses (Warren, 1967). Minimum flow discharged to the sea
The total annual average flow at the Mediterranean in both branches of the delta before the closure of the dam (in 1964) was ~ 3 5 km 3/yr. (Aleem, 1972; Sharaf el Din, 1977). The maximum average annual flow discharging to the sea was recorded as 55 km 3/yr. in 1879 and the minimum as 18 km 3 / yr. in 1913. Thus almost more than 35% of the annual amount of water passing through Wadi Halfa used to discharge to the sea. After the construction of the dam, some people believed that this water "wasted" to the sea should be entirely stored. However, a minimum amount of flow should be allowed to flow in order to maintain the river branches as efficient channels. If no water flows down these branches, they would be cultivated and might accumulate wind-blown dust (Hurst, 1952). Water infiltration from the Nile and the irrigation canals within the coastal zone is also necessary to maintain a balance between fresh and salt water. Lowering the rate of flow may increase the salt-water intrusion from the Mediterranean inland. These elements have not yet received serious investigations. Evaporation and seepage losses
At the early stages of planning the High Aswan Dam, the seepage losses were estimated between 1.0 to 2.0 km 3/yr. at a lake level of 180 m. Investigations made after the construction of the dam and the limited reports on this subject (Wafa and Labib, 1973) raised some doubts about their accuracy as explained in the following. Some people (Mosher, 1969) opposed the present site of the dam because of the existing geologic faults at the site of the dam that may lead to excessive leakage. This probably led some of the officials to attempt lessening the gravity of the leakage of the dam to the extent they claimed that the seepage would stop completely in the future after the silts have sealed the soil voids (Wafa and Labib, 1973). The authoI observed in Egypt between 1940 and 1945, when he was a district irrigation engineer, that the hydrographs of the subsoil water 10 km from the Nile had exactly the same pattern of the water-level stages in the river yet w:ith a time lag. This showed that even within the top layer which consists of silt--clay softs, the voids were never sealed through the past thousands of years. Wafa and Labib {1973) calculated also the bank storage in a crude non-scientific manner and estimated that at an elevation of 160 m
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(reached in 1970), a total of 16.225 km 3 would be lost by bank storage alone. However, examining Table I, with the additional data given by Waterbury (1979), it is obvious that during the period 1964--1971 the average annual values of inflow and outflow were respectively 83.3 and 66.9 km 3/yr. [(547 -- 78.5)/7]. This indicates an average annual loss of 16.4 km 3/yr. (seepage and evaporation) as compared to only 5.13 km s based on the data given by Wafa and Labib {1973). Meanwhile, it is surprising that tbe average outflow is already greater than the ultimate water requirements of Egypt by 1971 which was estimated at 62 km 3/yr. by EI-Madany (1968). If the estimates and records were correct, this excess of ~ 5 km 3/yr. must have been stored. Many reporters also questioned the possibility of ever reaching the full capacity of the dam (Sterling, 1972}. All the above-mentioned arguments indicate that the seepage and evaporation losses are poorly estimated. Most likely the seepage losses are too great, and in the author's opinion, this should not upset the managers of the dam. The lack of experience in groundwater development in the Nile Valley due to the available abundant surface water is obviously the main reason for improperly evaluating the seepage losses. The seepage losses were always neglected in the hydrological investi~a.*,ions of the Nile and only the evaporation losses were considered. It should be recognized that the evaporation losses are indeed real losses whereas seepage losses are actually gains to the groundwater reservoirs that can be recovered to supplement surface water if desired. Moreover, water stored from seepage around Lake Nasser may be very beneficial in the future to improve the complementarity between agricultural and power generation. With reference to water resources, Thomas and Revelle (1966)explained that: "full complementarity between agricultural use and power generation is not attainable because the seasonal water demand patterns for the two uses are different."
They further suggested that a high degree of complementarity could be achieved by providing additional storage below the dam and mentioned the possibility of underground storage. Accordingly, the seepage losses from Lake Nasser should be considered as a gain of major importance and benefits.
POTENTIAL REMEDIES
Not all the cited problems produced by the dam can satisfactorily and/or economically be solved. However, the main detrimental side-effects may have sound long-term solutions. In particular, spreading of malaria and schistosomiasis diseases and the erosion problems can be controlled by serious and tremendous effort. It seems that the drainage projects, now under implementation (Kashef, 1981) could lead to very satisfactory results. The water table would be lowered, preventing water logging and eventually controlling the diseases.
82 However, these projects should be coupled by improving irrigation wastes which resulted from the free irrigation system. As explained in the text, this is presently accomplished by lowering the water levels in the canals in such a way that the water is lifted for irrigation. It is claimed that about one-third of the land is presently irrigated in this manner (Clawson et al., 1971). At the present time it is estimated that ~ 1 3 . 5 km3 /yr. of drainage water is pumped to the Mediterranean Sea every year {Waterbury, 1979). This amount should decrease in the future after improving both drainage and irrigation practices. However, due to agricultural expansion it may not decrease below ~ 1 2 k m 3/yr. {Waterbury, 1979). This water has to be recycled, after mixing it with the proper fresh water to decrease its salinity, before it is transmitted to other locations where it is needed (Kashef, 1981}. Also in the future, after implementing the water projects in Sudan and other riparian countries (Kashef, 1981), additional water would be allocated to Egypt. Plans have to be made to make good use of this water without creating the present problems resulting from excessive water waste. The lack of the Nile silts after the closure of the Nile in 1964 resulted into the erosion of the Nile, drainage ditches and irrigation canals. This created a menace to thousands of barrages and bridges over these waterways. Their repair or replacement would amount to prohibitive costs. The erosion of the coastal areas threatened also the summer resorts, e.g., fish catch, and would lead to an increasing danger of salt-water intrusion due to the inland movement of the shoreline. It should be realized also that the lack of silt produced a financial burden by using chemical fertilizers to a gTeater extent than previously practiced. This should necessitate the release of Nile water to the sea over that required for irrigation in order to alleviate these effects and to maintain the Nile branches of the delta as active channels. In the author's opinion, the silt can be brought back to Egypt by constructing a channel (with tunnel segments if necessary) from the western side of Lake Nasser to the downstream of the dam (Fig. 1). The entrance and exit locations have to be determined by thorough site and hydraulic investigations. Across the entrance of this oroposed channel on the other side of the lake, a sloping (in plan) submerged weir may be constructed across the entire, or part of, the lake. This would help diverting the silts to the channel before it moves on to the dam. Because of the construction difficulties such diversion weirs may be constructed by dumping stones (as in rockfill dams or dikes used in river training): It was expected that after the construction of the High Aswan Dam, siltswould accumulate directly behind the dam. However, it has been observed that the silts accumulated near the southern portion of the reservoir. A survey of the location of the sediments together with proper site and hydraulic investigations should satisfactorily determine the alignment of both the proposed channel and weir. It is also suggested to make a branch to this proposed channel to feed the desert area known now as the "New Valley" in the Western Desert of Eg.vpt. The problems associated with this project are given in the preceding paper
83
(Kashef, 1981). The target of this project and other desert areas is to irrigate 77,000 feddans (Clawson et al., 1971). Although Clawson et al. stated that 50% of this target have already been reclaimed in the New Valley, Waterbury (1979} stated that only 3% of the target has been reclaimed. According to Roberts (1962), the cropped areas irrigated from groundwater (mostly fossil water) in the New Valley were 30,000, 20,000 and 100 feddans in the Dakhla, Kharga and Farafra oases, respectively. This total of 50,100 feddans is still almost the same as that reported by Wilcocks (1904) as 53,000 feddans, which obviously deteriorated through the years by the wind-blown dust and lack of water. The branch of the proposed channel would definitely be a sound solution for the current problems in these desert areas. The proposed channel and the diversion submerged weir would thus bring back the Nile silt to Egypt, thus increasing the fertility of the land and reducing the use of chemical fertilizers which would eventually produce water pollution. It would also prevent the continuing scour action in the coastal zones and within the Nile and other waterways. It would also save the fish catch, the expenses necessary to repair or replace the thousands of bridges and barrages and bring back the old status of the summer resorts along the Mediterranean. Objections may be raised as to the prohibitive costs of such proposed channel and weir, but in the author's opinion, such costs would definitely be less than those long-range uncertain remedies which would take longer time.
REFERENCES Aleem, A.A., 1972. Effect of river outflow management on marine life. Mar. Biol. (Berlin), 15(3): 200--208. Clawson, M., Landsberg, H.H. and Alexander, L.T., 1971. The Agricultural Potential of the Middle East. American Elsevier, New York, N.Y., 312 pp., 2 maps. EI-Madany, M.A., 1968. The regulation of the present Aswan Dam in conjunction with the High Dam. Int. Comm. on Irrigation and Drainage, 6th Congr., New Delhi, R. 13, Quest. 22, pp. 2 3 3 - 2 6 5 . Hammad, H.Y., 1972. River bed degradation after closure of dams. J. Hydraul. Div., Am. Soc. Cir.'Eng., Proc. Pap. No. 8814, 98(HY4): 591--607. Hurst, H.E., 1952. The Nile. Constable, London (rev. ed., 1957, 326 pp.). I.B.C. (International Board of Consultants), 1955. Sadd E1-Aaly Project, 1955. Sadd EIAaly Authority, Cairo, Nov. "1955, 44 pp., 2 plates. Jarvis, C.S., 1936. Flood stage records of the River Nile. Proc. Am. Soc. Civ. Eng., 62: 1012--1017. Kashef, A.I., 1981. The Nile -- one river and nine countries. J. Hydrol., 53:53--71 (this issue). Mosher, L., 1969. The dangers to a dam -- Aswan faces a test of its footing. The National Observer, Aug. 4, 1969, p. 4. Morrice, H.A.W. and Allan, W.N., 1959. Planning for the ultimate hydraulic development of the Nile Valley. Proc. Inst. Civ. Eng., London, 14: 101--287. Raheja, P.C., 1973. Lake Nasser. In: Man-made Lakes: Their Problems and Environmental Effects. Am. Geophys. Union, Geophys. Monogr., 17: 234--245.
84 Roberts, R., 1962. Reconnaissance Soil Survey. New Valley, Western Desert, Egypt, Cairo. Sharaf El Din, S.H., 1977. Effect of the Aswan High Dam on the Nile flood and the estuarine and coastal circulation pattern along the Mediterranean Egyptian coast. Limnol. Oceanogr., 22(2): 194--207. Sterling, C., 1972. Superdams: the perils of progress. Atlantic, 229(6): 35--41. Thomas, H.A. and Revelle, R., 1966. On the efficiency use of High Aswan Dam for hydropower and irrigation. Manage. Sci., 12(8): 296--311. Wafa, T.A.I. and Labib, A.H., 1973. Seepage losses from Lake Nasser. In: Man-made Lakes: Their Problems and Environmental Effects. Am. Geophys. Union, Geophys. Monogr., 17: 287--291. Warren, C.J., 1967. Two new dams augmenting Sudan's irrigated farmland. Foreign Agric., 5(26): 8--9. Waterbury, J., 1979. Hydropolitics of the Nile Valley. Syracuse University Press, Syracuse, N.Y., 301 pp. Willcocks, W., 1904. The Nile in 1904. E. and F.N. Spon, London, 225 pp. Wisely, W.H., 1972. People, ecology and the Aswan High Dam. Cir. Eng., 42(2): 37--39.
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Elsevier Scientific Publishing Company, Am:;terdam -- Printed in The Netherlands
[1]
TECHNICAL A N D ECOLOGICAL IMPACTS OF THE HIGH ASWAN DAM
ABDEL-AZIZ I. KASHEF*
Department of Civil Engineering, Yarmouk University, Irbid (Jordan) (Received July 30, 1980; accepted for publication October 8, 1980)
ABSTRACT Kashef, A.I., 1981. Technical and ecological impacts of the High Aswan Dam. J. Hydrol., 53: 73--84. Since the High Aswan Dam was planned in 1952 until it was completed in 1970, it was associated with numerous technical, social and political problems. The side-effects of the dam after its construction until the present time are the concern of various authorities all over the world. The technical and ecological impacts of the dam are discussed and the potential remedies are presented. A channel is proposed from the reservoir downstrean the dam with a branch to feed the Western Desert areas. The performance of the channel could be improved by a proposed submerged weir to divert the silts back to Egypt. The proposed remedy would bring back the fertility of the land, reduce the cost of chemical fertilizers, prevent erosion in the Nile and other waterways, stop the advance of the Mediterranean shoreline and would solve other social, technical and economic problems.
INTRODUCTION
The High Aswan Dam was one of a series of dams on the Nile that were constructed to improve the water-resources management since the nineteenth century. The first of these dams was known as the Qanater E1Khairia Barrage. This barrage consists of a set o f five barrages, ~ 25 km north of Cairo, and was used mainly as a diversion dam in order to feed high-level canals. Its operations started in 1886 for the main purpose of changing the basin irrigation system to a perennial system which allowed raising more than one crop a year, including cotton (Kashef, 1981). It is now serving as a touristic structure after the present Delta Barrage was built in the 1930's. In 1894, Sir William Willcocks (1904) proposed a storage dam at Aswan, a city located in a rainless region ~ 3 6 0 km north of Wadi Halfa (which is the m o s t remote town at the southern border of Egypt). The Aswan Dam was constructed between 1898 and 1902 with a storage capacity of 1 km 3 . It was heightened twice, in 1912 and 1934, to reach a maximum storage capacity of 5.3 km 3 .
* Formerly with the High Aswan Dam Authority, Cairo, Egypt, 1952--1954.
0022-1694/81/0000--0000/$02.50
© 1981 Elsevier Scientific Publishing Company
74
These two dams prompted the construction of an excellent net of irrigation and drainage canals. They were followed by other dams and barrages: (a) the Naga Hamadi, Esna, Assiut, Zifta and Edfina barrages in Egypt; (b) the Gebel Aulia and Sennar dams in Sudan; and (c) the Owen Falls Dam in Uganda. All these dams, with the exception of Owen Falls and the High Aswan dams, were designed on the basis of annual storage (Kashef, 1981). Water is stored yearly from the excess of the annual flood flow during the period August-January in order to use it during the subsequent period of low water supply from February to July. Shortly after the flood peak, the storage begins to minimize silt accumulation. In order to meet the ultimate water demands necessary for raising more crops in Egypt (the population increased from 2.5 million in 1840 to 40 million in 1979) and Sudan, additional water projects were suggested and some of the old barrages were strengthened. Some of the suggested dams had to be built outside Egypt. In order to avoid political implications, Adrian Daninos suggested a high dam a t Aswan with a huge capacity within the Egyptian territory. The idea was not at first appealling to the officials because of the prohibitive costs and also due to the lack of worldwide experience in dams of such capacity (164 km s ) which had to be built on a sand deposit 2 0 0 m thick rather than bedrock. Finally, the project reached the drawing board in 1952 after it had been recommended by the then newly established "National Production Council". The dam was constructed to provide long-term storage to meet the demands of agricultural expansion, to generate electricity, to guarantee water supply during the unexpectedly low-stage years and to protect the land from high floods. The optimistic program of agricultural land expansion in Egypt calls for irrigating an additional area of 1.5" 106 feddans*. The agricultural land in Egypt is limited within the Nile valley and few scattered desert areas. Thus the land expansion is limited to the desert areas alongthe valley borders and other unreclaimed areas in the delta that need excessive waters to make them productive. Other hopes included the diversion of the Nile water to the desert area beyofld the boundaries of the valley such as the series of oases in the Western Desert (known presently as the "New Valley Project"), the Sinai peninsula, and the Mediterranean coastal strip west of Alexandria.
H Y D R O L O G I C A L AND S T R U C T U R A L C O N S I D E R A T I O N S
The hydrological planning of a long-term (or hold-over or century) storage dam is by no means a routine matter. The reservoir capacity was estimated on the basis of an average flow over a number og selected consecutive years. This average should meet the water requirements downstream the dam. Although Nile records are available since the seventh century (Jarvis, 1936), A f e d d a n is an old E g y p t i a n land m e a s u r e m e n t ; 1 f e d d a n = 1.038 acre = 4 2 0 0 . 8 m : .
75 the average annual flows at Aswan (or Wadi Halfa) are irregular and unpredictable (Kashef, 1981). The design of the High Aswan Dam was based on an average of 84 km 3/yr. which was also used as the basis of the 1959 International Water Agreement between Egypt and Sudan. However, the actual average over a period of 30 years (1870--1899) was 109 km 3/yr. and that over the following fifty years (1900--1949) was 83 km 3/yr. Over a period of 95 years (1871--1965), the lowest average was 45.5 km 3/yr. in 1913 and the highest was 137.0 km 3/yr. in 1878 (Clawson et al., 1971). The water available for storage in a certain year would be the amount of flow in excess of the net average value which is computed from the selected gross average (84 km 3/yr.) reduced by the seepage and evaporation losses and also by the amount of water allocated to Sudan (a maximum of 15.5 km 3/yr. measured at Aswan according to the 1959 agreement). The loss in the reservoir was estimated as 11.0 km a/yr. (I.B.C., 1955). If in one year the flow is less than the selected average, water should be released from the reservoir to supplement the natural flow. If this happens frequently before the dam is full it would tremendously disrupt the planned water-management schedules. The planned maximum reservoir capacity of the High Aswan Dam is 164 km 3 when the water level reaches 1 S 2 m a.s.1. (or 9 7 m above river bed). However, after construction of tho dam, the actual losses were apparently greater than those estimated previously and the highest capacity of 115.0 km 3 was reached in October 1975 {Table I) at an elevation of 1 7 5 . 0 0 m (Waterbury, 1979}. Also many reports discarded the original design capa~:ity of 1 6 4 k m 3 and claimed that the maximum capacity should not exceed 1 5 7 . 4 k m a which as yet has never been attained (Waterbury, 1979). A breakdown of the revised maximum capacity of 157 km 3 is given in Table II. The reservoir of the dam is known as Lake Nasser in Egypt (Fig. 1) and as Lake Nubia for its southern portion located within the Sudanese territory. Its shortest length along the center line is 350 km in Egypt and 150 km in Sudan (Raheja, 1973). However, the total lengths of its shorelines are 8803 and 5960 km at elevations of 180 and 160 m, respectively. The length of the eastern shoreline is almost two times that of the western shoreline. At an elevation of 180 m, the maximum and mean depths are respectively 81 and 25 m; and the maximum and mean widths are respectively 25 and 17.95 km (Raheja, 1973). The lake has many khors or lagoons (arms), some of which reach more than 50 km in length. There axe 48 khors on the eastern side totalling 576 km in length and 37 on the western side with a total length of 394 km. The body of the dam itself lies on a deposit of 200 m thick sand underlain by granitic bedrock. It consists of a main rockfill dam connected with two cofferdams of smaller sizes, one upstream and one downstream. Between the river banks the length is 3600 m at the top and 5 2 0 m at the bottom. The widths of the dam axe 980 m at the bottom and 40 m at the top and its height
127.60 132.70 142.45 151.25 156.55 161.30 164.88
175.00 182.00
1964--1965 1965--1966 1966--1967 1967--1968 1968--1969 1969--1970 1970--1971
Total Average Oct. 1 9 7 5 Never a t t a i n e d
582.901 83.27 ---
119.430 79.550 69.120 92.370 71.102 69.539 81.790
Inflow* 1 (km 3 )
547.003 78.143 ---
119.082 78.497 67.760 87.290 62.740 61.263 70.371
O u t f l o w and accumulation -*1 in reservoir (km 3 )
S o u r c e s : ,1 Wafa and L a b i b ( 1 9 7 3 ) ; , 2 W a t e r b u r y ( 1 9 7 9 ) .
Maximum reservoir height* 1 (m)
Period
D a t a o n s t o r a g e and losses for t h e High A s w a n ' D a m , E g y p t
TABLE I
35.896 5.128
0.348 1.053 1.360 5.080 8.362 8.276 11.417
Actual reservoir losses* 1 (km 3 )
13.9 15.3--16.7
9.4 78.5 3,500
115.0 157.4
5.9 41.1 2,200
5,168 6,200
1.4
Estimated evaporation losses .2 (km 3 ) 9.8
Reservoir v o l u m e .2 (km 3 )
550
(kin ~ )
surface .2
Reservoir
77 T A B L E II Breakdown of the revised m a x i m u m reservoir capacity ( k m 3 ) of the Aswan D a m (a) Share of Egypt d o w n s t r e a m the d a m (including 30 k m 3 for hydroelectric power) (b) Share of Sudan measured at Aswan or "~20.5 k m 3 in t h e areas of irrigation (Morrice and Allan, 1959); if this is totally used it should be d e d u c t e d ; t o the best of the a u t h o r ' s knowledge, Sudan is using at present ~ 5.5 k m 3 after the construction o f the Roseires and Khashm el Girba dams in Sudan (Kashef, 1981) (c) Evaporation and seepage losses (d) Volume of silt deposits accumulated through hundreds of years (e) Long-term storage for irrigation and flood control
55.5
18.5 11.0 30.0 42.0 Total
157.0
~ Nile
. ~@A Kom Ombo swan Darn
branch t o oases (Western
Desert
Loke N a s s e r"~
A
Ibrirn
Abu 2 /
'
^~,~Tushka
S i m b e l L~" ~ ¢ _ J~a EGYPT
Adinan
SUDAN
f~ Lake Nubia
A - E n Ior'g'ed
Fig. 1. The reservoir of the High Aswan Dam existing of Lake Nasser (Egypt) and Lake Nubia (Sudan}.
78
is 111 m above the river bed. The upstream cofferdam is 600 m long and 50 m high, while the downstream cofferdam is 5 0 0 m long and 30 m high. The dam contains a total of 4 3 " 1 0 6 m 3 of materials which would be equivalent to 17 times the volume of Cheop's pyramid or 25 times the volume of the Empire State Building in New York City (Wisely, 1972}. In order to prevent seepage losses beneath the dam a huge grout curtain, 2 0 0 m deep, was constructed. The construction of the dam started on January 9, 1960 and was completed in 1968. The closure of the Nile t o o k place, for the first time, in :/964. The Aswan power station consists of twelve turbo generators able to churn out 0.175"106 kW-hr, each (total 2.1"106 kW-hr.) and fed by tunnels discharging 1.0 km 3/day (Wisely, 1972). The construction of the power station was completed in 1970 on the east side of the river. In the original plans (I.B.C., 1955), diversion channels with tunnel segments were suggested on the western side of the river. Also a horizontal impervious blanket in the upstream was proposed. Both designs were eliminated by the financiers (U.S.S.R.) who also wished to eliminate the grout curtain but were strongly opposed by the Egyptian engineers. Altt~ough it seems that no serious side-effects were developed from the elimination of the horizontal blanket, the elimination of the diversion channels on the western side produced serious problems to the country and its people as explained in the following section.
SIDE-EFFECTS OF THE DAM
:ilting and erosion The annual total sediments passing Wadi Halfa were estimated between 100"106 and 140'106 t (Aleem, 1972). The released sediments from Aswan were estimated at 26.2"106 , 5.5"106 and 3"106 t/yr. during 1964 (closure of the Nile), 1965 and 1966, respectively (Hammad, 1972). All sediments are presently deposited in the southern region of Lake Nasser. The released clear water with its high velocities starts to pick up sediments from the river bed: ~ 1 1 " 1 0 6 and ~6"106 t/yr. during 1965 and 1966, respectively, from Aswan to Cairo; a distance of ~ 9 6 5 km (Hammad, 1972). It was reported that 88% of the sediments were carried to the sea before constructing the High Aswan Dam and ~ 9 % were deposited on the land. Assuming that the specific weights of the deposited silt vary from 1.12 to 1.6 t / m 3 , the annual decrease in water storage would roughly vary between 62.5~106 and 125"106 m 3 . The lower figure (62.5"106 m 3 ) may have been used in designing the capacity of the High Aswan Dam where silt storage was estimated at 30 km 3 in 500 years (I.B.C., 1955). The present lack of silt in Egypt leads to excessive erosion in the river channel and the Nile delta region due to the high velocities of clear water.
79
Some research workers believe that the scour action may stabilize in the future (Hammad, 1972). In the author's opinion, this may be true yet after the damage has been done. It has also been reported (Wisely, 1972) that three low-head dams are planned between Aswan and Cairo at a cost of US $100 million to alleviate the degradation process. {This idea was recently discarded.)
Socio-economic impacts Social and economic side-effects of the High Aswan Dam include drastic losses in the fish industry, gradual deterioration of the main summer resorts along the Mediterranean, the spread of diseases and the migration of entire villages which were inundateci by the reservoir of the dam. Before the construction of the dam, the annual fish catch from the Nile, the lakes, the Mediterranean and Red Sea was estimated at 1 2 . 5 - 1 0 4 t (Aleem, 1972). The sardinella catches have dropped because of the lack of silt from 1.5"104 t in 1964 to 0.46°104 t in 1965. It dropped further in 1966 to only 554 t. It is expected, however, to catch 2-104 t annually from Lake Nasser. The extremely hot weather at the site of the dam and the long distance from the main market (Cairo and the Nile delta) would add more problems to lessen the effects of this partial loss recovery. The rapid erosion of the northern summer resorts due to the lack of silts and the high velocities of clear water is threatening the beaches and the recreation industry, especially near Damietta and Rosetta, including the famous resort of Alexandria. Economic losses have already been reached in these areas. The conversion of the basin irrigation system to perennial in southern Egypt led to spreading of the malaria and schistosomiasis (bilharzia) diseases for the first time in these areas. As a mat'~er of fact, the conversion in southern Egypt started at a very slow rate during World War II but it could not be c,ompleted without additional water. In some farms shallow artesian wells were used to supplement the basin irrigation and raise more than one crop a year. Because of the expenses of these wells, the water was used wisely and the diseases were not so widely spread as at the present time where water runs in the canals and flows over the land by gravity (free of charge). A b o u t 106 acre (4047 km 2 ) of land in the Nile Valley were still under basin irrigation in 1950 and their conversion is almost complete (Clawson et al., 1971). The over-use of water by farmers and the resulting diseases are now closely watched by the government. Small pumps and hand-lifting tools (based mainly on the Archimedian screw principle) are used at present in areas where water is intentionally lowered in the irrigation canals (Kashef, 1981). A large-scale drainage project (cost b U S $600 million) has been initiated to lower the high water table which resulted from the gravity irrigation procedure. This would definitely help to confine spreading of diseases.
80 Due to flooding of the land south of Aswan, 100,000 persons from the Nubian region were resettled in Kom Ombo (a plateau 46 km north of Aswan and on the east side of the river) in 16,548 houses scattered over 43 newly constructed villages (Wisely, 1972). Additionally, 500,000 Nubians were resettled in Sudan in 1962 in Khashm el Girba with their 18,000 heads of livestock; twenty villages were constructed with 250 houses (Warren, 1967). Minimum flow discharged to the sea
The total annual average flow at the Mediterranean in both branches of the delta before the closure of the dam (in 1964) was ~ 3 5 km 3/yr. (Aleem, 1972; Sharaf el Din, 1977). The maximum average annual flow discharging to the sea was recorded as 55 km 3/yr. in 1879 and the minimum as 18 km 3 / yr. in 1913. Thus almost more than 35% of the annual amount of water passing through Wadi Halfa used to discharge to the sea. After the construction of the dam, some people believed that this water "wasted" to the sea should be entirely stored. However, a minimum amount of flow should be allowed to flow in order to maintain the river branches as efficient channels. If no water flows down these branches, they would be cultivated and might accumulate wind-blown dust (Hurst, 1952). Water infiltration from the Nile and the irrigation canals within the coastal zone is also necessary to maintain a balance between fresh and salt water. Lowering the rate of flow may increase the salt-water intrusion from the Mediterranean inland. These elements have not yet received serious investigations. Evaporation and seepage losses
At the early stages of planning the High Aswan Dam, the seepage losses were estimated between 1.0 to 2.0 km 3/yr. at a lake level of 180 m. Investigations made after the construction of the dam and the limited reports on this subject (Wafa and Labib, 1973) raised some doubts about their accuracy as explained in the following. Some people (Mosher, 1969) opposed the present site of the dam because of the existing geologic faults at the site of the dam that may lead to excessive leakage. This probably led some of the officials to attempt lessening the gravity of the leakage of the dam to the extent they claimed that the seepage would stop completely in the future after the silts have sealed the soil voids (Wafa and Labib, 1973). The authoI observed in Egypt between 1940 and 1945, when he was a district irrigation engineer, that the hydrographs of the subsoil water 10 km from the Nile had exactly the same pattern of the water-level stages in the river yet w:ith a time lag. This showed that even within the top layer which consists of silt--clay softs, the voids were never sealed through the past thousands of years. Wafa and Labib {1973) calculated also the bank storage in a crude non-scientific manner and estimated that at an elevation of 160 m
81
(reached in 1970), a total of 16.225 km 3 would be lost by bank storage alone. However, examining Table I, with the additional data given by Waterbury (1979), it is obvious that during the period 1964--1971 the average annual values of inflow and outflow were respectively 83.3 and 66.9 km 3/yr. [(547 -- 78.5)/7]. This indicates an average annual loss of 16.4 km 3/yr. (seepage and evaporation) as compared to only 5.13 km s based on the data given by Wafa and Labib {1973). Meanwhile, it is surprising that tbe average outflow is already greater than the ultimate water requirements of Egypt by 1971 which was estimated at 62 km 3/yr. by EI-Madany (1968). If the estimates and records were correct, this excess of ~ 5 km 3/yr. must have been stored. Many reporters also questioned the possibility of ever reaching the full capacity of the dam (Sterling, 1972}. All the above-mentioned arguments indicate that the seepage and evaporation losses are poorly estimated. Most likely the seepage losses are too great, and in the author's opinion, this should not upset the managers of the dam. The lack of experience in groundwater development in the Nile Valley due to the available abundant surface water is obviously the main reason for improperly evaluating the seepage losses. The seepage losses were always neglected in the hydrological investi~a.*,ions of the Nile and only the evaporation losses were considered. It should be recognized that the evaporation losses are indeed real losses whereas seepage losses are actually gains to the groundwater reservoirs that can be recovered to supplement surface water if desired. Moreover, water stored from seepage around Lake Nasser may be very beneficial in the future to improve the complementarity between agricultural and power generation. With reference to water resources, Thomas and Revelle (1966)explained that: "full complementarity between agricultural use and power generation is not attainable because the seasonal water demand patterns for the two uses are different."
They further suggested that a high degree of complementarity could be achieved by providing additional storage below the dam and mentioned the possibility of underground storage. Accordingly, the seepage losses from Lake Nasser should be considered as a gain of major importance and benefits.
POTENTIAL REMEDIES
Not all the cited problems produced by the dam can satisfactorily and/or economically be solved. However, the main detrimental side-effects may have sound long-term solutions. In particular, spreading of malaria and schistosomiasis diseases and the erosion problems can be controlled by serious and tremendous effort. It seems that the drainage projects, now under implementation (Kashef, 1981) could lead to very satisfactory results. The water table would be lowered, preventing water logging and eventually controlling the diseases.
82 However, these projects should be coupled by improving irrigation wastes which resulted from the free irrigation system. As explained in the text, this is presently accomplished by lowering the water levels in the canals in such a way that the water is lifted for irrigation. It is claimed that about one-third of the land is presently irrigated in this manner (Clawson et al., 1971). At the present time it is estimated that ~ 1 3 . 5 km3 /yr. of drainage water is pumped to the Mediterranean Sea every year {Waterbury, 1979). This amount should decrease in the future after improving both drainage and irrigation practices. However, due to agricultural expansion it may not decrease below ~ 1 2 k m 3/yr. {Waterbury, 1979). This water has to be recycled, after mixing it with the proper fresh water to decrease its salinity, before it is transmitted to other locations where it is needed (Kashef, 1981}. Also in the future, after implementing the water projects in Sudan and other riparian countries (Kashef, 1981), additional water would be allocated to Egypt. Plans have to be made to make good use of this water without creating the present problems resulting from excessive water waste. The lack of the Nile silts after the closure of the Nile in 1964 resulted into the erosion of the Nile, drainage ditches and irrigation canals. This created a menace to thousands of barrages and bridges over these waterways. Their repair or replacement would amount to prohibitive costs. The erosion of the coastal areas threatened also the summer resorts, e.g., fish catch, and would lead to an increasing danger of salt-water intrusion due to the inland movement of the shoreline. It should be realized also that the lack of silt produced a financial burden by using chemical fertilizers to a gTeater extent than previously practiced. This should necessitate the release of Nile water to the sea over that required for irrigation in order to alleviate these effects and to maintain the Nile branches of the delta as active channels. In the author's opinion, the silt can be brought back to Egypt by constructing a channel (with tunnel segments if necessary) from the western side of Lake Nasser to the downstream of the dam (Fig. 1). The entrance and exit locations have to be determined by thorough site and hydraulic investigations. Across the entrance of this oroposed channel on the other side of the lake, a sloping (in plan) submerged weir may be constructed across the entire, or part of, the lake. This would help diverting the silts to the channel before it moves on to the dam. Because of the construction difficulties such diversion weirs may be constructed by dumping stones (as in rockfill dams or dikes used in river training): It was expected that after the construction of the High Aswan Dam, siltswould accumulate directly behind the dam. However, it has been observed that the silts accumulated near the southern portion of the reservoir. A survey of the location of the sediments together with proper site and hydraulic investigations should satisfactorily determine the alignment of both the proposed channel and weir. It is also suggested to make a branch to this proposed channel to feed the desert area known now as the "New Valley" in the Western Desert of Eg.vpt. The problems associated with this project are given in the preceding paper
83
(Kashef, 1981). The target of this project and other desert areas is to irrigate 77,000 feddans (Clawson et al., 1971). Although Clawson et al. stated that 50% of this target have already been reclaimed in the New Valley, Waterbury (1979} stated that only 3% of the target has been reclaimed. According to Roberts (1962), the cropped areas irrigated from groundwater (mostly fossil water) in the New Valley were 30,000, 20,000 and 100 feddans in the Dakhla, Kharga and Farafra oases, respectively. This total of 50,100 feddans is still almost the same as that reported by Wilcocks (1904) as 53,000 feddans, which obviously deteriorated through the years by the wind-blown dust and lack of water. The branch of the proposed channel would definitely be a sound solution for the current problems in these desert areas. The proposed channel and the diversion submerged weir would thus bring back the Nile silt to Egypt, thus increasing the fertility of the land and reducing the use of chemical fertilizers which would eventually produce water pollution. It would also prevent the continuing scour action in the coastal zones and within the Nile and other waterways. It would also save the fish catch, the expenses necessary to repair or replace the thousands of bridges and barrages and bring back the old status of the summer resorts along the Mediterranean. Objections may be raised as to the prohibitive costs of such proposed channel and weir, but in the author's opinion, such costs would definitely be less than those long-range uncertain remedies which would take longer time.
REFERENCES Aleem, A.A., 1972. Effect of river outflow management on marine life. Mar. Biol. (Berlin), 15(3): 200--208. Clawson, M., Landsberg, H.H. and Alexander, L.T., 1971. The Agricultural Potential of the Middle East. American Elsevier, New York, N.Y., 312 pp., 2 maps. EI-Madany, M.A., 1968. The regulation of the present Aswan Dam in conjunction with the High Dam. Int. Comm. on Irrigation and Drainage, 6th Congr., New Delhi, R. 13, Quest. 22, pp. 2 3 3 - 2 6 5 . Hammad, H.Y., 1972. River bed degradation after closure of dams. J. Hydraul. Div., Am. Soc. Cir.'Eng., Proc. Pap. No. 8814, 98(HY4): 591--607. Hurst, H.E., 1952. The Nile. Constable, London (rev. ed., 1957, 326 pp.). I.B.C. (International Board of Consultants), 1955. Sadd E1-Aaly Project, 1955. Sadd EIAaly Authority, Cairo, Nov. "1955, 44 pp., 2 plates. Jarvis, C.S., 1936. Flood stage records of the River Nile. Proc. Am. Soc. Civ. Eng., 62: 1012--1017. Kashef, A.I., 1981. The Nile -- one river and nine countries. J. Hydrol., 53:53--71 (this issue). Mosher, L., 1969. The dangers to a dam -- Aswan faces a test of its footing. The National Observer, Aug. 4, 1969, p. 4. Morrice, H.A.W. and Allan, W.N., 1959. Planning for the ultimate hydraulic development of the Nile Valley. Proc. Inst. Civ. Eng., London, 14: 101--287. Raheja, P.C., 1973. Lake Nasser. In: Man-made Lakes: Their Problems and Environmental Effects. Am. Geophys. Union, Geophys. Monogr., 17: 234--245.
84 Roberts, R., 1962. Reconnaissance Soil Survey. New Valley, Western Desert, Egypt, Cairo. Sharaf El Din, S.H., 1977. Effect of the Aswan High Dam on the Nile flood and the estuarine and coastal circulation pattern along the Mediterranean Egyptian coast. Limnol. Oceanogr., 22(2): 194--207. Sterling, C., 1972. Superdams: the perils of progress. Atlantic, 229(6): 35--41. Thomas, H.A. and Revelle, R., 1966. On the efficiency use of High Aswan Dam for hydropower and irrigation. Manage. Sci., 12(8): 296--311. Wafa, T.A.I. and Labib, A.H., 1973. Seepage losses from Lake Nasser. In: Man-made Lakes: Their Problems and Environmental Effects. Am. Geophys. Union, Geophys. Monogr., 17: 287--291. Warren, C.J., 1967. Two new dams augmenting Sudan's irrigated farmland. Foreign Agric., 5(26): 8--9. Waterbury, J., 1979. Hydropolitics of the Nile Valley. Syracuse University Press, Syracuse, N.Y., 301 pp. Willcocks, W., 1904. The Nile in 1904. E. and F.N. Spon, London, 225 pp. Wisely, W.H., 1972. People, ecology and the Aswan High Dam. Cir. Eng., 42(2): 37--39.