|Long Distance Water Transfer: A Chinese Case Study and International Experiences (UNU, 1983)|
Chairman, Water Research Centre
Ministry of Irrigation, Cairo, Egypt
SOME 5,000 years ago, there existed in Egypt a civilization which is still the wonder of mankind. Many factors contributed towards the creation of this civilization, among which were religious impulses, brilliant brains, and a high degree of human discipline and devotion. The principal factor, however, which enabled this civilization to develop was the River Nile, which brought, and still brings, water and fertility into a country which would otherwise be a desert.
Egypt has practically no rain and its agriculture depends on irrigation from the Nile. In no country in the world would a single waterway play so important a role in the economic and social development of a nation as does the River Nile in Egypt.
The total area of Egypt is about 100 million ha, of which only a little over 2.5 million ha are now cultivated. With multiple cropping, the cropped area reaches about 4.75 million ha per year.
Despite advances in industrialization and increased urbanization, agriculture still accounts for 50 per cent of the total population, 47 per cent of the employment, about 30 per cent of the gross national product, and 80 per cent of export earnings.
However, Egypt is now facing a major challenge of how to increase the rate of growth in agriculture production to generate and meet its future food requirements to cope with a very high annual rate of increase in population (2.5 per cent). The population which numbered about 20 million in 1952 is now estimated at 41 million and is expected to reach 70 million by the year 2000.
The share of cultivated land per capita has dropped from 0.163 ha in 1930 to 0.071 ha in 1978. In spite of the fact that an area of about 0.42 million ha has been reclaimed since 1952, an area exceeding 250,000 ha has been lost to industrial and urban uses. To keep the present level of per capita share of the cultivated land, new areas amounting to about 62,500 ha per annum have to be reclaimed.
Egypt's major water transfer projects are considered in this chapter, with brief discussion on the impact of such projects on Egyptian agriculture.
THE RIVER NILE
The River Nile is one of the most remarkable geographic features of Africa. Its catchment area covers 2,900,000 km², it extends from latitude 4°S to latitude 31°N, and experiences a great variety of climate (figure 1). The vegetation within the Nile basin is varied, and includes alpine flora in the higher parts, dense tropical forest, tall elephant grass, savanna forest, thick vegetation of tropical swamps, thorny forests and scanty desert vegetation. Also there are dense crops grown on irrigated lands.
In general, the Nile basin can be divided into four main sub-basins: (1) The White Nile, whose head waters rise south of the Equator, and whose runoff is 29 per cent of the total Nile runoff. Its water is clear. (2) The Atbara River, which rises in North Ethiopia, is a flashy river. It is dry for half the year, and its runoff is muddy and constitutes 14 per cent of the total Nile runoff. (3) The Blue Nile, which also rises in North Ethiopia, has runoff equal to 57 per cent of the total runoff of the Nile. The flow is muddy during the rainy season. (4) The Main Nile flows northward to the sea. The river is the longest in the world, being about 6,700 km long. Its source is at an altitude of 5,120 m above m.s.a. in Central Africa while its estuary is in the Mediterranean Sea. Its course traverses the countries of Uganda, Kenya, Tanzania, Rwanda, Burundi, Zaire, Ethiopia, as well as Sudan and Egypt.
Extending from Aswan 24°N latitude and to the north, the Nile valley takes the shape of a long and narrow strip of land until the apex of the delta 30°N latitude, a distance of nearly 900 km. The maximum width of the valley hardly exceeds 25 km. It is enclosed on both sides between arid and desert plateaus which extend on the one hand to the Red Sea and on the other hand to the Egyptian-Libyan borders across the Sahara.
A few km to the north of Cairo begins the Delta or lower Egypt, which is composed of three parts (figure 2). The first, which is the Delta proper, is comprised of the two branches of the Nile.
The two branches are the only two now remaining of the seven ancient arms, the Rosetta arm on the west and the Damietta on the east. The five other branches have been modified and included in the system of irrigation canals. The Delta forms a triangle with an altitude of 160 km and a base of 140 km.
The second part of the Delta lies to the west of the Rosetta arm, with the shape of an elongated triangle whose apex is a little below the separation of the two arms of the Nile and whose base along the sea extends about 70 km in length.
The third part stretches to the east of the Damietta branch. It also forms a triangle whose base along the sea is 160 km.
"Egypt is the gift of the Nile." So said Herodotus, the ancient
Greek historian. It can bestow goodness when it floods in one year, while in
another year nothing but drought and privation may prevail. In flood time, its
flow is more than sufficient, but in the summer it is unable to satisfy Egypt's
The annual Nile flood varies considerably from one year to the other. Its yield may reach 151 x 109 m³ as in 1978 or may drop to 42 x109 m³ as in 1913. The flood usually occurs in summer from August to October and during this period, it may vary from 36 x 109 m³ to 7 x 109 m³.
Losses from the Nile channel differ from time to time according to the water level in the Nile and adjacent groundwater levels in the valley's aquifers which are hydrologically connected to the Nile bed and sides. When the groundwater levels are higher, water seeps to the Nile and is considered as a gain. Generally, studies conducted recently in Egypt indicated that the net value of losses and gains of the river channel between Aswan and the Delta (about 1,000 km) represent an amount of water revenue of about 1.5 x 109 m³.
The Egyptians, in ancient and modern times, have always contemplated and observed the nature of the river with anxiety. But when they discovered its source, they were able to better understand its nature and characteristics.
Engineering efforts to control the Nile started during the Pharaonic epoch, when King Mina, who ruled Egypt in the 1st Dynasty, constructed the left bank to protect urban areas. Then he went on constructing canals and bridges to carry the Nile water to lower lands behind the newly constructed bank.
During the 12th Dynasty, Sesostris continued what Mina had started. He constructed the right Nile bank, then transformed Lake Morris into a reservoir where the flood water is diverted to reduce its violence and to protect the Delta lands. The lake has since become the flourishing governorate of Fayoum. More recently in 1833, there emerged the idea of constructing two main barrages on the Damietta and Rosetta branch canals upstream.
The concept of annual storage, referring to the retention of part of the flood water after the flood peak is reached, was first introduced to the Nile system by Egyptians in 1898. The construction of the old Aswan Dam began end was completed in 1902. Its storage was 1 X109m³. It was designed to ensure the provision of sufficient water during the following summer when the Nile yield decreases. This system is repeated year after year. Because of the annual flood, yield may vary considerably and, as stated earlier, the filling of the reservoir is not ensured every year. Indeed, in some years it may not be filled at all.
The Assiut and Zifta Barrages were established in the year 1902, to be followed by Esna Barrage in 1906 (figure 1).
In 1912, the Aswan Dam was heightened to increase its annual storage capacity to 2.5 X 109 m³. A second heightening of the dam took place in the year 1913 to increase the annual storage capacity to 5 x109 m³.
In 1920, Egypt convened a joint committee, comprising representatives from the Egyptian and British governments and the International Consulting Bureau, to study the suggested plan and to propose the basis for the fulfilment of irrigation needs of Sudan. In 1929, the Egyptian and the British governments concluded the Nile Water agreement (on behalf of the Nile Basin countries) on the basis of the joint committee's recommendations. This agreement stipulated that the construction of any works on the river, its tributaries or its source, that might obstruct the flow of the Nile and affect Egypt's right to exploit such water for her benefit was not permissible. The agreement also stipulated the distribution of the Nile waters between Egypt and Sudan.
In 1932, a further agreement was concluded between Egypt and Sudan according to which Egypt had the right to construct Gabal El Awlia reservoir in Sudan to store 3.5 x 109 m³ with the annual benefit of 2.5 x 109 m³ at Aswan, to irrigate 250,000 ha during the summer. The programme included the reclamation of 170,600 ha in lower Egypt, the reclamation and conversion of 218,500 ha in Upper Egypt and the guarantee of rice cultivation in an area ranging between 80,000 and 146,000 ha per annum.
Many ammendments were made to these programmes, for different reasons. Circumstances during the Second World War required expansion in the production of cereals and food products.
In 1947, a technical committee of senior irrigation officials met to restudy the river control projects, in order to face future agricultural expansion for the period ending 1975. The committee submitted a comprehensive plan that was adopted by the Government in 1949. The plan suggested long-term storage in the Equatorial lakes and Lake Tana, in addition to other projects to minimize water losses in swamp regions of Sudan, estimated at about 50 per cent of the natural yield reaching the region, conversion of some basin irrigated lands to perennial, and reclamation of about 0.75 million ha.
While the Ministry of Public Works was preparing for the execution of the major projects in the plan, the 1952 revolution broke out, and the idea of long-term storage at Aswan was adopted. It was necessary to create an artificial lake site on the river, which could retain the surplus water of the high flood years, releasing only what was needed to meet the deficit of low flood years. This lake needed an additional capacity to provide for sedimentation and to receive high flood water.
Therefore, the idea of constructing the High Dam south of the Aswan reservoir received great attention from the Revolution, and the project took priority in the series of River Control Projects. In the meantime, Sudan outlined a plan for agricultural expansion in El Gezira, including the construction of El Roseris reservoir on the Blue Nile.
Talks were held to reach agreement with Sudan concerning the redistribution of the Nile water. In November 1959, an agreement was concluded between the two countries regarding the full utilization of the water. It stipulated that the net benefit from the High Dam shall be calculated on the basis of the average natural river yield at Aswan in the years of this century, which is estimated at 84 x 109 m³ per year: The acquired rights of the two countries (48.0 for Egypt and 4.0 for Sudan) and the average losses from the High Dam storage are to be deducted from this yield; and the balance shall be the net benefit to be divided between the two countries. This benefit shall be divided into a ratio of 14.5 x 109 for Sudan and 7.5 for Egypt. The annual losses of storage in the Dam are estimated to be 10 x 109 m³. By adding these shares to the acquired rights, the share for Sudan is 18.5 x 109 m³, and 55.5 x 109 for Egypt.
The agreement states also the establishment of a joint technical authority between both countries to study, outline and approve any future development of the Nile water in Sudan and Egypt.
Indeed, this agreement has become a successful model of cooperation between countries sharing the same river basin. More African Nile Basin countries are encouraged to participate in this technical cooperation.
OLD NILE RIVER WATER TRANSFER PROJECTS
Irrigation requirements also enabled the ancient Egyptians to build navigable canals. To avoid the dangers in the south, King Merner (2400 BC) constructed the first canal at Elephantine, which was afterwards widened and deepened by Sesostris III of the 12th Dynasty (1875 BC). This canal, protected by fortresses, commanded the trade with Nubia.
Several attempts were made to construct a canal connecting the Nile and the Red Sea. They never succeeded, mainly due to the storms in the Gulf of Suez causing problems to their primitive sea-going ships. Shortly after the Arabs came to Egypt in the 7th century, they made new attempts to revive the canal, but their trials soon failed for the same reason.
In the early years of the 19th century, Mohammed Aly attempted to bring order to the country: cultivable lands were surveyed and distributed among the people. The introduction of field crops and vegetables necessitated a radical change in the irrigation system. It was, at that time, indispensable to dig deep canals to conduct the low level water of the summer to the lands under cotton in addition to protecting them against inundation until the plants were brought to full maturity. This was the origin of perennial irrigation in Egypt.
Very deep canals about 8 m below ground level were required for summer conditions and they were filled each year with silt deposits requiring a great deal of clearance work to be carried out annually. To avoid this recurring nuisance the construction of barrages was suggested, to hold up the low summer water and raise it artificially to flow into the canals without clearing their beds to such great depths. The construction of the first barrage (Delta) started in 1843 and was completed in 1861.
Three main canals, called Rayahs, had also been dug, the first to irrigate areas east of the Delta, the second to the middle and the third to the west. Soon the Delta had an extensive network of canals varying in size to distribute water to every part of it (figure 2).
The old river branches disappeared and only the two big arms of the Nile, the Damietta and Rosetta, remained. Every new canal was provided with a system of control works, which made regulation and distribution of water possible, and each canal received a fair share of the available supply according to the area served.
The cultivated area in the Delta which was partially irrigated under the perennial system amounted to about 0.833 million ha in 1843. Subsequent to the construction of the Delta Barrages and the spread of the irrigation network the area reached 2.5 million ha with a cropping intensity of about 2.0 million ha.
By virtue of the two successive agreements between the Egyptian government and the Suez Canal company in 1854 and 1856 for the purpose of creating a navigable waterway between the Nile and the Suez Canal, to furnish water for irrigation of some lands, and to provide drinking water for towns and stations established along its course, the Ismailia Canal was constructed. The canal has its inlet from the Nile at Cairo and runs directly as far as the town of Ismailia, where it bifurcates into two arms; one to the north to feed the town of Port Said and the second to the south to the town of Suez.
The canal was constructed in 1862. It is 128 km long, and for much of its length was constructed through sandy strata. Its top water level is significantly above the surrounding land. Particularly in the sandy areas there is a significant amount of seepage from the canal and this has contributed to the relatively high water table in the adjoining land. The original canal depth is reported to have been 2-4 m and its width about 18 m.
Regarding Upper Egypt, in 1873 the Ibrahimia canal was dug to irrigate Middle Egypt all the year round. In 1900 it supplied perennial irrigation to 29,000 ha and basin irrigation to another 175,000 ha. With its head regulator on the left bank of the Nile near Assint, the canal runs for a distance of 61 km where it divides into four branches: Bahr Yusif, Deiruieh, Ibrahimia extension and Sahilia. Bahr Yusif runs for a distance of 278 km before it enters the Fayoum which depends entirely upon Bahr Yusif for its supply.
ASWAN HIGH DAM
The Aswan High Dam is a rockfill dam with a total length of 3,600 m and a height of 111 m above the river bed. Its width is 980 m at the bottom and 40 m at the top. The reservoir storage capacity is 162 X 109 m³ distributed as follows:
90 x 109 m³ for live storage;
31 x 109 m³ capacity for sediments deposits over 500 years;
41 x 109 m³ as flood room for protection against high floods.
The length of the reservoir lake is about 500 km with an average width of 10 km. The dam is provided with a hydroelectric power station with an installed capacity of 2.4 million kw or about 10,000 million kwh per annum.
The construction of the dam started in 1960 and was completed in 1970. Egypt's water share of 7.5 x 109 m³ was utilized in reclaiming 0.417 million ha and converting 375,000 ha from basin system to perennial irrigation besides increasing rice and sugar-cane cultivation in the country.
Major Impacts of the High Dam
The execution of the Aswan High Dam was preceded by very extensive feasibility studies. It was a scheme of colossal dimensions, calling for heavy expenses and envisaging ambitious objectives. Some of the impacts of the High Dam have negative effects, but these are far outweighed by the benefits achieved.
Protection against High Floods and Droughts
Today, more than 10 years after the completion of the Dam, Egypt is protected against dangerous floods such as those of the years 1964, 1967 and 1975. The dam also saved the agricultural crops during a very low water year of 1972/73.
The Dam became the keystone for future agricultural expansion both vertically and horizontally. The control and better distribution of water released all the year round improved the summer irrigation and allowed the increased production of many crops.
Before the construction of the High Dam 0.417 million ha in Upper Egypt were under basin irrigation. Land under this system is flooded once every year with a water head of one metre for about 40 days. One crop could be produced under this system every year. The conversion of the area to perennial irrigation was completed after the High Dam and two to three crops a year can now be cultivated.
Environmental Impacts of the High Dam
(a) The terrestrial system was changed into an aquatic system with the
inundation of vast areas of land. Though rather thinly populated, people had to
be relocated from their traditional homes to new ones. It also inundated land
rich in historical monuments, which had to be dismantled and moved to other
higher locations. Among these are Abu Simbel and Philae temples.
(b) The riverine system was changed into a lacustrine one, i.e. 500 km of the River Nile was transformed into a huge water reservoir extending across the borders of Egypt and Sudan.
(c) So far as water quality is concerned, the main changes following the construction of the Aswan High Dam have been due to suspended solids, dissolved solids, and algae content. These changes are the results of physio-chemical and biological transformations occurring in the reservoir, i.e. sedimentation, evaporation, and primary production. At the present time water released from the reservoir is silt-free and its suspended solids content is due to phytoplankton, estimated at 107 to 10 cells per litre. The increase in the silt content as the Nile water reaches Cairo is due to river erosion and agriculture return flow. A salt balance simulation model was developed using hydrological data from 1913 to 1977. Evaporation in the reservoir results in an 8 to 15 per cent increase in the total dissolved solids content of the released water.
Siltation in the Lake
Prior to the construction of the Aswan High Dam, the Nile discharged between 60 and 180 million tons of silt annually into the Mediterranean. Since 1964, this amount of sediment has been held in the reservoir. The main concerns have been the effect of sedimentation on the capacity and shape of the reservoir, river bed erosion, and erosion of the Mediterranean coastline. Since 1968 sedimentation has been confined to the southern one-third of the reservoir. Results of the field surveys and satellite imagery indicate that extensive sediment deposits up to 25 to 30 m in thickness are accumulating in Sudan near Wadi Halfa. The continued accumulation of sediments will result in changes in reservoir morphology, which will affect the storage capacity, surface area, evaporation losses, and shoreline configuration. It is estimated that the total dead storage of the reservoir (for silt deposition) may be consumed in a period of not less than 500 years.
Observation of reservoir bed levels shows that siltation is decreasing from year to year and most of it is now taking place at the far upstream end of the reservoir. During the flood of 1971, the concentration of silt became negligible at the section situated 250 km upstream from the Dam.
Degradation Downstream of the Aswan Dam
As a result of sediment deposition in the newly created reservoir, degradation problems were expected in the river channel from Aswan to the Mediterranean. This problem was the subject of intensive studies before and after the construction of the Dam. Observations and investigations were carried out.
The river below the dam is now controlled by 5 old barrages. A drop in water levels, slopes and bed configuration has been closely observed in the reaches between these barrages. The maximum bed scour recorded downstream of the barrages is shown in Table 1.
The extent and rate of degradation in the future has been estimated by different approaches and measures for control and river bed protection were proposed. An additional escape spillway is under construction on the left bank at Tashka, about 200 km upstream from the High Dam, to release excessive high floods. This project will help in recharging groundwater aquifers of the Nubian sandstone in the western desert.
Table 1 Maximum Bed Scour downstream of Barrages
|Site||Drop in Water Levels in cm|
|Distance from |
|at Q = 90 million m³/day||at Q = 200 million m³/day|
|DS Nag Hammadi||359||26||71||37||44|
Effects of Loss of Silt on Agriculture
Studies on Nile silt have revealed the following:
(a) The silt-loaded water flows only during the flood season and more than 88
per cent of the Nile silt used to be released to the sea with the excess flood
(b) Two-thirds of the remaining 12 per cent of the silt was precipitating on cultivated lands under the basin irrigation system in Upper Egypt. After the High Dam these basin lands were converted to perennial irrigation, and thus they no longer receive flood water.
(c) The nutritive value of the Nile silt has been investigated as regards its azote content. It was found that azote did not exceed 0.13 per cent of the weight of the silt. One-third of this was found to be of value to plant nutrition. This loss could be compensated by about 13,000 tons of calcium nitrate fertilizer which is now being produced in Aswan, utilizing the power generated from the dam.
The absence of flood silt has modified the technology of land reclamation of sandy soils in Egypt. Silt depositions used to improve soil characteristics for surface irrigation. Different field irrigation methods are now applied for such sandy soils.
Some reports have claimed that the High Dam will seriously affect the fish catch from the Mediterranean shores at the mouths of the two river branches at Rosetta and Damietta, as it will impede the flow of silt and consequently reduce the numbers of fish previously attracted by nutritive elements contained in the silt. Shortage of sardines has been reported during the last few years. But this variety has never constituted a major percentage of the total catch in Egypt. The main catch comes from the relatively freshwater, northern lakes occupying an area of more than 200,000 ha. These lakes are still fed by agriculture drainage water.
On the other hand, the High Dam Lake which has a surface area of 5,000 km² and constitutes a major aquatic resource has become one of the main fish resources in Egypt. The total catch from the lake in 1976 was estimated at 20,000 tons. There is still a shortage of fishing facilities, which if made available could bring the catch to 100,000 tons/year. More than 50,000 fishermen are now operating along the shores of the lake.
Investigations on reservoir fish indicate that the Tilapia species are most abundant in fish landings, followed by Latus niloticus and cat fish and syprinids, represented by Labea and Barbus species. Recently, Tilapia galilaea, which was sporadically recorded in the early years of the impoundment has become the most abundant species in fish landings. These fish are periphyton and plankton feeders and they formed 75 per cent of the total fish landing in 1978, as compared to 27 per cent in 1968.
Public Health Impacts
The extension of irrigation and drainage networks and the change from basin to perennial irrigation in Upper Egypt is believed to increase the potential for aquatic snail vectors of schistosomiasis. Schistosomiasis has been a chronic problem in Egypt. Parasite's eggs have been found in mummified viscera from Tutenkhamon's tomb.
It was estimated that the cost of controlling schistosomiasis transmission in Egypt by use of molluscides is about $3.4 per ha annually. The introduction of covered field drainage systems in Egypt on a large scale and the inclusion of health control components in such new projects will help in the eradication of the disease.
For thousands of years, Egypt's agriculture was essentially confined to a narrow strip along the Nile River and to the fan-shaped Delta. The present cultivated area is about 2.5 x 106 ha, accounting for 2.5 per cent of Egypt's total area.
The reclamation and development of new lands has been a major and costly aspect of agricultural policy in Egypt for the past 25 years. The increased quantity of irrigation water available from the High Dam, mounting population pressures in old land areas, and a substantial number of landless farmers, despite the allocations made under the Land Reform Programme, all encouraged the expansion of the agricultural land base. Thus, both economic and political pressures supported the high priority given to developing new lands. In some cases the emphasis on capital investments in land, both old and new, has diverted needed capital investment from other inputs such as credit, fertilizers, extension and research.
The soil, water and climate of many desert areas in Egypt are such that agriculture is technically feasible all the year around, if adequate management and support services exist.
The Ministry of Irrigation, in its general policy statement for the National Programme of Irrigation adopted in 1978, has estimated that horizontal expansion encompassing 1.2 million ha of new lands will be completed by the year 2000.
From the point of view of providing these areas with irrigation water, several water transfer projects were proposed. Part of this plan depends on enlarging existing canals to accommodate new water needs, and the second part involves the construction of new waterways. The major irrigation works are as follows:
(i) enlargement of Ismailia Canal;
(ii) West Nubaria Canal System;
(iii) El Salam Canal.
Enlargement of Ismailia Canal
Information on the past enlargement of the canal is limited but several regulators were built in the 1870s and were remodelled in the 1920s to allow a greater flow.
Over the next 20 years Egypt intends to expand agricultural production substantially in the Ismailia Canal Zone. To this end the Ismailia Canal is being widened to increase the canal capacity from 135 m³/sec to 439 m³/sec so as to provide for the expansion of water supplies to extend the area to be irrigated from 131,000 ha to 0.46 million ha. Originally it was intended that the widening would be carried out in three stages but the plans were revised and widening will now be completed in two stages. Along the canal there are several offtakes having vertical lift gates operated by the Ministry of Irrigation.
During the past 10 to 15 years high water table levels have been recorded in the old and new lands of Egypt and among the many reasons reported are the increase in water application and lack of field drainage. Some waterlogged areas are reported along the Ismailia Canal. In certain stretches seepage is another factor contributing to high water tables. The enlargement of the canal has caused the cut off of the low permeable layers of clay deposited along the sides and beds of the canal during recent years. This has caused the total seepage rate to increase from 17.0 to 22.4. m³/sec after the completion of the second stage.
Studies have been conducted to find out the most economical way of overcoming the loss of fresh water through seepage, considering the different alternatives of using the seeped water to replenish the groundwater aquifers of the area. It was concluded that lining the canal, which is an expensive task under the existing water conditions, is not the most economical solution along the path of the canal.
Pumping from existing drains into the canal, where about 56 per cent of the total predicted seepage water could be recovered, and tubewells delivering water directly to the area of land reclaimed north and south of the canal provide the most economical solutions. When water becomes a scarce resource canal lining on some sections would also be marginally economical. This lining should be strong enough to withstand wave erosion caused by motorized barges
West Nubaria Canal System
The West Nubaria Project, situated some 50 km southwest of Alexandria, covers an area of approximately 208,000 ha representing 40 per cent of all the new lands whose reclamation has been made possible by the construction of the Aswan High Dam. At present some 25,000 ha of the area are either being cultivated or are under reclamation.
The Nile water is delivered to the northwestern part of the Delta through two large main canals: Rayah El Behera and Nubaria. In connection with the new west Nubaria project, these canals are insufficient. Investigations have indicated the possibility of using the Nubaria, after some modifications, as a carrier for water requirements of the west Nubaria project. Side by side with reclamation processes, the widening of the Nubaria Canal was initiated. It remains only to determine the method of supplying the Nile water from the Rosetta branch to the Nubaria Canal.
The Ministry of Irrigation has conducted several studies to determine the most feasible solution. Four alternatives were considered:
(i) construction of a new barrage on the Rosetta Branch near Kafr El
(ii) widening of the Rayah El Behera to hold the extra water required for reclaimed areas;
(iii) construction of a pumping station at Zawiet El Bahr, to feed Rayah El Behera with the excess water requirements;
(iv) construction of a new canal Rayah El Nasseri parallel to Rayah El Behera.
Each alternative was considered in detail, including studies of side effects and advantages. Among the most important factors studied were:
(i) the effect of the construction of a new barrage on the water table
conditions in the Delta, and the cost of the corresponding drainage
(ii) socio-economic impacts on people living in the area to be occupied by widening of existing canals or constructing new ones;
(iii) improving irrigation conditions in certain parts of the central Delta;
(iv) guaranteeing navigation in the Rosetta Branch.
It was finally decided that the proposal of constructing a new barrage should be rejected due to the impacts of such a barrage on raising the water table levels in a considerable part of the Delta. The proposal of constructing a new big canal parallel to Rayah El Behera was adopted and the construction of this canal was completed in 1971.
The Rayah El Nasseri runs almost parallel to Rayah El Behera for a stretch of 56 km through a newly constructed channel. Then the next 25 km pass through an old canal course followed by a new reach of 2 km, which terminates in the Nubaria Canal.
The Nubaria water level is 4 to 5 m above sea level. Since the project area west of the canal rises gradually to elevations as high as 10 to 60 m above sea level, all the water needed is pumped by a series of electrical pumping stations which are interconnected by the Nasser lined canal. Irrigation water is then distributed by a series of branch canals and some secondary pumping stations.
The Nasser Canal is partially constructed and will have a capacity of 116 m³/sec. A total of five pumping stations will be built, three of which have already been completed and put into operation. These pumping stations will eventually lift the water from the Nubaria Canal to a maximum elevation of 60 m above sea level. The total length of the canal is 150 km.
The groundwater levels were at a depth of 20 to 60 m when land reclamation in the area started in 1968. It was thought at that time that groundwater problems would not be experienced for a long time. Groundwater studies on a large scale were postponed to a later date after the major reclamation works were to be completed. But very soon after irrigation took place in 1968, a rapid rise in water tables and severe groundwater and salinity problems were reported. The water table gradually rose in some areas to less than 2 m below the ground surface. Over a period of three years, the water table rose 12 m or an average of 4 m per year. High electric conductivity values (as high as 32,000 micro mhos/cm) have been reported in some wells, the major components being Na, Mg, Cl and S04. This saline groundwater started to flow towards the Nubaria main irrigation canal. Outflow of saline groundwater into some of the principal irrigation canals also took place.
The problems were thoroughly investigated and it was found that the main reasons are:
(ii) seepage from the main canals and the conveyance system;
(iii) the presence of gypsum layers close to the soil surface in many parts of the area.
An interceptor drain was dug parallel to the canal and a short distance from it to collect some of the salty groundwater. This solution was found to be of very limited value.
A recent inspection of the Nubaria Canal shows that it suffers severely from erosion. The problem is mainly brought about by the high speed of the barges using the canal. The bow waves set up by these craft contribute to the erosion of the banks. The maximum speed of the canal craft considered in the bank design was 8 kph, whereas some craft were recorded as travelling at 20 kph.
There are two proposals to overcome this difficulty: one by reducing the speed of the barges to the point where the bow wave will cause negligible scour (a difficult exercise to implement and wasteful in terms of transport efficiency); the second is to line the banks with a scour prevention apron, thereby increasing the stability of the banks but allowing the present usage of the canal to continue without alteration.
El Salam Canal
Within the plan for the reclamation of 1.2 million ha, 0.63 million ha are located in eastern Delta and north of Sinai. To supply this area with irrigation water, two projects were proposed. The first comprises the enlargement of Ismailia Canal, and the second suggests the construction of the new El Salam Canal to irrigate a new area of 250,000 ha. The canal starts upstream from the proposed Faraskur barrage on the Nile Damietta Branch; 83,000 ha are located west of the Suez Canal and 167,000 ha east of the canal in the northern plains of the Sinai Desert.
After the intake of the canal, it travels southeast 82 km to the Suez Canal, crosses the Canal by a tunnel and then extends parallel to the coastal city of ElAresh.
The Canal water is going to be a mixture of fresh and drainage water. About 2.4 X 109 m³ of drainage water from the eastern part of the Delta will be utilized annually through mixing with fresh Nile water. There will be two mixing pumping plants along the course of the canal, with a mixing ratio of 1:1. The salinity of the mixed water will not exceed 800 ppm.
The project feasibility study has been completed and it was decided to implement the project in two stages. The first will cover the stretch from the Nile to the Suez Canal to irrigate the 167,000 ha. The total estimated cost for the first phase of the project is $175 million.
SOME MAJOR CONSTRAINTS TO EGYPTIAN AGRICULTURE
Lack of On-farm Water Management
One of the pressing problems in Egypt is that farmers, who for thousands of years had access to water only during the flood season and hence stored all they could get at that time, use excess water that is currently available all the year round from the controlled flow of the High Dam. The problem is accentuated by the fact that no charge is made for the irrigation water and minimum control is exerted during the "on" periods when water is available in particular canals.
Calculations have indicated that in 1974 potential contributions to water table, equivalent to 0.42 m of water depth over the entire cultivated land of Egypt,resulted from over-irrigation. Controlled availability of water permits the growing of two to three crops annually, where only one was grown before, thus increasing the problems associated with excess water use.
In 1960, about 0.83 million ha suffered from salinity. The area affected by waterlogging and salinity has been increasing at an alarming rate over the past 10 years. This has occurred on both old and new lands.
If traditional irrigation continues to take place, more areas will be affected. Management measures and new capital investments are necessary on all of this land to maintain these problems at tolerable levels.
Waterlogging and Salinity
A massive programme for drainage of the affected areas is underway. Tile drains have been installed on 700,000 ha so far. Drains are scheduled to be installed to cover a total area of 2.1 million ha by the year 1989. Mechanical techniques for laying the plastic pipes are adopted.
Soils in the Nile valley and Delta are among the most fertile in the world, with 90 per cent of the old lands in classes I, II and III. With new problems of drainage and salinity these classes could be affected. Another programme of soil amelioration by use of subsoiling, deep-ploughing and addition of gypsum is in effect now in areas that suffer badly from salinity problems.
Salinity and waterlogging on reclaimed land are basically due to the lack of an adequate drainage system. When the irrigation system was planned and implemented, critical drainage problems were not expected for 10 to 15 years. Hence, no urgency was felt to implement a drainage system at that time but the need for an adequate drainage system is now apparent.
Improved Irrigation Systems
Efficient use of irrigation water is one of the most important agricultural water management practices needed in Egypt today.
The bulk of Egypt's agricultural land is irrigated by traditional methods. Over the years, a system of small basins formed by a network of low dikes or bunds, into which water is delivered by a series of small hand-dug ditches, has developed for perennial irrigation. Most farmers must lift water from the depressed irrigation canals to the farm level by means of simple, traditional devices.
Efficient use of irrigation water through improved and controlled delivery systems, improved irrigation methods, and on-farm water management are the main concerns of several national programmes initiated in Egypt during the past five years.
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