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2.2 The Tigris and Euphrates Rivers

Despite the great size of the Middle East, there are only three rivers that can be classified as large by world standards-the Nile, the Euphrates, and the Tigris. The watersheds of both the Euphrates and the Tigris are situated within the Middle East, predominantly in the countries of Turkey, Syria, and Iraq (fig. 2.11).

The Euphrates, which is the longest inter-state river in western Asia, has been developed since 4000 B.C. Several ancient civilizations in Mesopotamia were supported by basin irrigation from the Tigris and Euphrates Rivers. Owing to the extremely arid climate, however, the farm lands on the Mesopotamian alluvials have suffered from salt accumulation and waterlogging problems since 2400 B.C., during the Sumerian age. This ancient civilization disappeared with the abandonment of irrigation-canal systems. The washing out of accumulated salts, or leaching as it is called, can be carried out only with an efficient

Fig. 2.11 The Tigris-Euphrates basin drainage system, which requires careful water management to sustain the irrigation system.

Before Turkey began building large dams on the Euphrates, the river's average annual flow at the Turkish-Syrian border was about 30 x 109 m. To this, a further 1.8 x 109 m is added in Syria from the Khabour River, a major tributary. On several occasions in recent years, low water levels in the Lake Assad reservoir, behind the Tabqa dam, have restricted the hydro-power output (with installed capacity of 800 MW) and irrigation development. In the longer term, a reduction in Euphrates water entering the country could be a major constraint on Syrian power generation and agriculture. Iraq used to receive 33 x 109 m of river water per year at Hit, 200 km downstream from the Syrian border before the 1970s, when both Turkey and Syria built a series of large dams on the Euphrates River. By the end of the 1980s, the discharge decreased to as little as 8 x 109 m per year at Hit. By 1989, 80% of the natural run-off of the Euphrates River had been developed by adding a third large dam, the Ataturk, which is the largest dam in Turkey, with a gross reservoir storage volume of 48.7 x 109 m (effective volume, 19.3 x 109 m).

The development of the Euphrates, which has problems of both quantity and quality, such as the increasing salinity in the internal delta downstream, is examined to distinguish the complexities, commonalities, and conflicts over riparian issues which put the peace of the world at risk.

Historically, development was limited to the semi-arid and arid zones of the lower reaches of the Tigris and Euphrates. The valleys of the two rivers encompass the northern portion of the famous "Fertile Crescent," the birthplace of the Mesopotamian civilizations. Owing to salt accumulation, waterlogging, and poor management of the canal system, the irrigated lands were progressively abandoned and the old civilizations declined.

The water resources of the Euphrates River have been almost fully developed since the 1970s by construction of the large dams at Keban, Karakaya, Karababa/Ataturk, and Tabqa on the upper and middle reaches of the main stream. Eighty per cent was reached by adding the Ataturk dam in 1989.

2.2.1 The river basin

The Tigris-Euphrates basin lies primarily in three countries-Turkey, Syria, and Iraq (see fig. 2.11). Both the Tigris and Euphrates rivers rise in the mountains of southern Turkey and flow south-eastwards, the Euphrates crossing Syria into Iraq and the Tigris flowing directly into Iraq from Turkey. The main stream of the Euphrates in Turkey is called the Firat, and it has four major tributaries-the Karasu, the Murat, the Munzur, and the Peril After leaving Turkey, the Euphrates has only one large tributary, the Khabur, which joins the main stream in Syria. By contrast, the Tigris has four main tributaries, all of which unite with the main stream in Iraq. The largest of these, the Great Zab, has its source in Turkey, while the Lesser Zab and the Diyala originate in Iran. All of the catchment of the Adhaim, which is the smallest stream, is in Iraq. In southern Iraq the Tigris and the Euphrates unite to form the Shatt al-Arab, which in turn flows into the Arabian Gulf.

The lengths of the main streams are 2,330 km for the Euphrates, 1,718 km for the Tigris, and 190 km for the Shatt al-Arab. The catchment area of the basin is 423,800 km, of which 233,000 km is that of the Euphrates, 171,800 km of the Tigris, and 19,000 km of the Shatt al-Arab (Shahin 1989).

The hydrographic and hydrological characteristics vary greatly over the basin. Rainfall in the Turkish headwaters area is abundant, but seasonal. However, from about 37N, the river runs through arid country in Syria and Iraq.

2.2.2 Hydrology

The main sources of the Euphrates river flows in Turkey are found in the four tributaries, all of which originate at altitudes of about 3,000 m or more in the mountainous areas of eastern Turkey. Hydrological study was initiated in 1927-1929 by installing the first pluviometric stations in the basin of the Firat, the uppermost part of the Euphrates. Long-term records indicate an average annual precipitation of about 625 mm in the Keban basin, decreasing to approximately 415 mm in the lower Firat basin.

The upper part of the Euphrates basin has a catchment area of 63,874 km at the confluence of the Firat and the Murat near the Keban, which produces 80% of the total annual flow at Karababa/ Ataturk (fig. 2.12). The average flow at Keban station over the 31 years of records (1936-1967) was 648 m/sec, with the lowest flow of 136 m/sec in September 1961 and the maximum flood of 6,600 m/sec in May 1944. The long-term annual average discharge at the Karababa/Ataturk dam site is estimated to be 830 m/sec. (Doluca and Pircher 1971).

The Firat has a relatively regular regime, characterized by two months of very high average flow in April and May and a period of eight dry months from July to February. The annual flow varies considerably from year to year, including extremely low flow records between July 1957 and January 1963, during which the average flow decreased to only 83% of the long-term average. The average winter flows, varying between 200 and 300 m/sec, increase in February from early spring rains at lower elevations. The increase continues during March, when the snow begins to melt, and in April and May monthly average flows of 2,000 m/sec and more are reached, with maximum floods occurring between mid-April and early May under the combined effect of melting snow and rains. The flow rapidly diminishes after June, reaching its minimum values in September and sometimes October.

Fig. 2.12 Upper Euphrates River basin: Firat and Murat

The flows of the Tigris and Euphrates in Iraq are largely dependent on the discharges in Turkey. Much of the discharge of the Tigris results from the melting snow accumulated during the winter in Turkey. However, winter rains, which are common in late winter and early spring, falling on a ripe snowpack in the highlands, can greatly augment the flow of the main stream and its tributaries, giving rise to the violent floods for which the Tigris is notorious. The period of greatest discharge for the Tigris system as a whole is from March through May and accounts for 53% of the mean annual flow. The highest mean monthly discharge takes place during April. Minimum flow conditions are experienced from August through October and make up 7% of the annual discharge. The mean annual flow of the Tigris is 48.7 x 109 m in total at its confluence with the Euphrates, which includes 13.2 x 109 m from the Greater Zab, 7.2 x 109 m from the Lesser Zab, and 5.7 x 109 m from the Diyala (Shahin 1989; Beaumont et al. 1988).

The total flow of the Euphrates is not as great as that of the Tigris, although the river regimes are similar. It, too, rises in the highlands of Turkey and is fed by melting snows, to an even greater extent than the Tigris, but it lacks the major tributaries which the Tigris has. In Iraq, the period of maximum flow on the Euphrates is shorter and later than that of the Tigris and is usually confined to the months of April and May. Discharge during the two months accounts for 42% of the annual total. Minimum flows occur from August through October and contribute only 8.5% of the total discharge. The mean annual runoff of the Euphrates is 35.2 x 109 m at its confluence with the Tigris (Shahin 1989; Beaumont et al. 1988).

These mean values, however, conceal the fluctuations in discharge that can occur from year to year, for it must be remembered that both floods and drought are themselves of variable magnitude. Schematic regime hydrographs of the Tigris and Euphrates are shown in fig. 2.13.

2.2.3 Euphrates River development and salinity problems

The Euphrates River, which is the longest multinational river in Westem Asia, has been developed since 4000 B.C. Several ancient civilizations in Mesopotamia were supported by basin irrigation from the Tigris and Euphrates Rivers. Owing to the extremely arid climate, however, the farm lands on the Mesopotamian alluvials have suffered from salt accumulation and waterlogging problems since Sumerian times. These ancient civilizations disappeared with the abandonment of irrigation-canal systems.

Fig. 2.13 Selected regime hydrography of the Tigris and Euphrates Rivers (Source: Beaumont et al. 1988)

One of the major reasons for the success of this complex irrigation network was the establishment of an efficient system of drainage, which prevented waterlogging of the soil and consequent salination of the land. Throughout the lowland as a whole, drainage was achieved by supplying irrigation water from the Euphrates in the west and the Nahrawan canal in the east (fig. 2.11). This permitted the Tigris, which was situated between the two, to function as a drain, and to collect water from the adjacent agricultural lands. So efficient was this system that it supported widespread cultivation of the land in the region for many years without a serious decline in land quality. The maximum limits of agricultural expansion in the Diyala plains seem to have been attained during the Sassanian period (A.D. 226-637). With the collapse of Sassanian rule, a marked deterioration in agricultural conditions occurred, which continued almost unchecked for centuries. The reasons for the agricultural decline are complex, but a major one was probably the decreasing effectiveness of the central government, which meant that the necessary reconstruction and maintenance of the irrigation networks tended to lapse. Progressive siltation of the major canals occurred, reducing the efficiency of water transmission, and the irrigation control works fell into disrepair. By the time of the Mongol invasions of the twelfth and thirteenth centuries A.D., the abandonment of the once fertile land was almost complete.

The term "hydraulic civilization" has been used to describe societies similar to those in the alluvial lowlands of Iraq, which required large scale management of water supplies by the bureaucracies of central governments for widespread agriculture to be feasible.

Although the agricultural recovery of the Tigris-Euphrates lowlands began during the late nineteenth century, with the rehabilitation of a number of the ancient canals, it was not until the early part of the twentieth century that the first modern river-control work, the Al-Hindiyah barrage (1909-1913) was constructed on the Euphrates. Its original function was to divert water into the Al-Hillah channel, which was running dry, but later, following reconstruction in the 1920s, it was also used to supply other canals. Between the two world wars, considerable attention was given to the Euphrates canal system, and many new channels were constructed and new control works established. Development on the Tigris tended to come later. The building of the Al-Kut barrage began in 1934 but was not completed until 1943, while on the Diyala, a tributary of the Tigris, a weir was constructed in 19271928 to replace a temporary earth dam that had to be rebuilt each year following the winter flood. The weir allowed six canals to be supplied with water throughout the year.

Following the Second World War, river-control schemes tended to concentrate on the problems of flood control. Two of the earliest projects, completed in the mid-1950s, were situated towards the upper part of the alluvial valley. The Samarra barrage was constructed on the Tigris River with the objective of diverting flood waters into the Tharthar depression to provide a storage capacity of 30 x 109 m. A similar scheme was also built on the Euphrates, where harthar depression to the Al-Ramadi barrage diverted flood waters into the Habbaniyah reservoir and the Abu Dibis depression. It had been hoped that stored water from these two projects might be used for irrigation during the summer months, but it was discovered that the very large evaporation losses, together with the dissolution of salts from the soils of the depressions, seriously diminished water quality and rendered it unsuitable for irrigation purposes. In conjunction with the barrages on the main streams themselves, two major dams were constructed on tributaries of the Tigris. The Dukan dam, with a reservoir storage capacity of 6.3 x 109 m, was completed on the Lesser Zab River in 1959, while further south, on the Diyala River, the Darbandikhan dam, with 3.25 x 109 m of storage, was opened in 1961.

The Tigris and Euphrates Rivers are the main sources of water in Iraq. Because of flood irrigation, 1,598,000 ha of land have been affected by salinity, and the government is trying to reclaim this land (fig. 2.14). Before the 1970s, when both Turkey and Syria built a series of large dams on the Euphrates, Iraq received 33 x 109 m of river water per year at Hit, 200 km downstream from the Syrian border. By the end of the 1980s, the flow discharge at Hit had decreased to as little as 8 x 109 m per year (WPDC 1987).

Before Turkey began building large dams on the Euphrates, the river's average annual flow at the Turkish-Syrian border was about 30 x 109 m. To this, a further 1.8 x 109 m is added in Syria from the Khabur River (Beaumont 1988). On several occasions in recent years, low water levels in the Lake Assad reservoir, behind the Tabqa dam (fig. 2.11), have restricted the hydro-power output (with an installed capacity of 800 MW) and irrigation development. In the 1970s Syria was planning to reclaim 640,000 ha or more in the Euphrates basin. However, progress has been slow, and only about 61,000 ha of new land either has been brought into cultivation or will be in the near future. The water requirement for this area is minimal and can at present easily be supplied from the 12 x 109 m Lake Assad reservoir or from the river's flow. In the longer term, however, a reduction of the Euphrates water entering the country could be a major constraint on Syrian power generation and agriculture.

In 1989, 80% of the natural run-off of the Euphrates River was developed by closing the Ataturk dam, the biggest dam in Turkey, with a gross reservoir storage volume of 48.7 x 109 m (effective volume, 19.3 x 109 m) as shown in fig. 2.12.

Fig. 2.14 Salinity map of the Tigris-Euphrates delta (Source: Beaumont et al. 1988)

2.2.4 The Peace Pipeline project

An inter-basin development plan was studied in the context of Turkey's ambitious "Peace Pipeline" project in 1987, which would include the transfer of fresh water from the Seyhan, Ceyhan, and Euphrates basins by a series of dams and diversion tunnels to supply countries in the Arabian peninsula, including Syria, Jordan, Saudi Arabia, Kuwait, Bahrain, Qatar, the United Arab Emirates, and Oman (fig. 2.15). The Peace Pipeline would have a total length of about 6,550 km and a capacity of 6 million m per day.

Fig. 2.15 The Peace Pipeline scheme

The unit cost of water pumped along the Peace Pipeline has preliminarily been estimated at US$0.84-US$1.07 per m (Gould 1988). The economic viability of the project was assessed by comparison with conventional seawater desalination. The unit water cost of the seawater desalination was simply assumed at US$5/m (Gould 1988). This, however, is not likely to represent the actual desalination cost, which should now take into account recent advances in membrane technologies for desalination such as reverse osmosis (see sections 2.8 and 2.9).

2.2.5 Political constraints and feasibility

Fresh water supplies are finite, and it is becoming more and more difficult to undertake projects that include the shifting of available water supplies to new areas of demand, especially if the project involves crossing political boundaries. The Peace Pipeline will probably not be a key application for individual states but an option in water-resources planning at a multinational level.

The total project cost of the Peace Pipeline has been estimated at US$21 x 109 (1990 price, Economist 1990), which would make it one of the most expensive transboundary projects in the world (compare the Euro tunnel, at US$15 x 109; the Itaipu dam, US$9 x 109; the Mediterranean-Dead Sea solar-hydro project, US$2 x 109).

Water politics will be a key issue in transboundary river development in the Middle East. There is as yet no political commitment to the Peace Pipeline, but this project and variations on it remain options for consideration in the ongoing peace process.

2.3 The Indus River

The Indus, one of the mightiest rivers of the world and the second longest in western Asia, has a mean annual discharge of 207.5 x 109 m (ECAFE 1966). The Indus River system has ten times the volume of flow of the Colorado River in the United States and Mexico, and more than three times that of the Nile.

Alluvial plains in the middle to lower reaches of the Indus system have been developed to form the largest irrigation scheme in the world. Approximately 16,000 km of canals have been constructed to irrigate over 9 million ha (Buras 1967). This irrigation project covers the greater part of a vast plain covered with fine-textured alluvial soil overlying coarser sediments extending deep (ten to hundreds of metres) downward to the bedrock of an ancient valley.

The development of the irrigation project was mostly carried out after 1850, but elements of an ancient flood irrigation channel can still be found. Most of the canals were excavated through the surface soil to the more pervious underlying fine sand, so that a large proportion of the surface water diverted through these canals seeped underground. The sediment, which forms an extensive aquifer, was continuously recharged by the leaking irrigation canals, so that the groundwater table rose continuously. In many areas, this rise was estimated to be approximately 30 cm per year. As a result, in much of the Indus plain the groundwater level was near the soil surface. Proper aeration of the soil could not take place, and, with the prevailing arid climatic conditions, capillary action and evapotranspiration moved salts from the subsurface up to the root zone of crops and to the land surface. Thus once-fertile lands have so deteriorated that crops can no longer be grown. In the 1950s and 1960s, the salinity and waterlogging problems became so serious that intensive research was carried out by international agencies, headed by the Harvard University Water Resources Group, focusing on aquifer utilization and management, including the mining of groundwater.

During successive stages of development of the irrigation systems in the Indus valley, little attention was given to land drainage, and emphasis was put on maximizing the extent of irrigated land. Integrated management of the underlying aquifer system in line with the surfacesubsurface drainage is now being used successfully to control salinity and reclaim irrigated land.

2.3.1 The river basin

The Indus rises in Tibet, in the snow-clad Kailas range of the Himalayas, about 5,500 m above mean sea level. The catchment area extends over four countries-China, India, Pakistan, and Afghanistanwith the portion in Pakistan accounting for more than 50% of the total. The Indus basin lies in the subtropical zone; the Tropic of Cancer passes through its southernmost part, while its northern edge reaches the latitude 37N (see fig. 2.16).

The Indus cuts through mountain ranges forming a narrow gorge and deep channel from the headwaters until an important tributary, the Kabul River, joins it from the west near Attock. A few kilometres above the town of Mithankot, the Indus is joined by its most important tributary, the Panjnad River, which carries the waters of five main tributaries-the Jhelum, the Chenab, the Ravi, the Beas, and the Sutlej. The river slope from the headwaters to Attock is approximately 1/ 300; from Attock to Mithankot it is 1/4,000; and from Mithankot to the sea it averages 1/7,000. The total length of the Indus is about 2,900 km. The drainage area of the whole system is approximately 970,000 km.

Fig. 2.16 The Indus River basin

The northern region of the basin, where the Indus and its main tributaries originate, is fully covered with rugged sky-high mountains and glaciers, comprising an area of about 452,000 km. Because of the steep and barren slopes of these mountains, the erosion is very heavy, ranging according to locality from about 400 to over 4,000 tons per km annually, with an average of about 1,500 tons. Lower down, the basin comprises vast plains formed and separated from each other by the five main tributaries. Further down from Mithankot, the Indus valley is covered with alluvium built up by the deposition of silt carried down by the river. The delta begins from Kotri, about 185 km from the sea, where the land is almost level and the soil is generally infertile. Closer to the sea is marshy land and mangrove forests which are generally flooded during high tides.

2.3.2 Hydrology

As noted, the Indus basin lies in the subtropical zone. In the plains, the average temperature during winter is about 21C in Karachi and about 15C in Lahore. Summer, the hottest season, is from May to August, and average temperature ranges from about 29C in May to about 34C towards the end of June or early July, when the maximum temperature often rises above 27.7C. Despite the mighty Indus, the Indus plain is semi-arid. There are significant extremes of rainfall in the basin. The area around Sukkur and Mithankot receives only about 100 mm of rain a year, while, at Murree, a hill station at 2,280 m elevation, the annual precipitation is about 1,270 mm. The precipitation, inclusive of snow, is many times heavier in the hilly region than in the plains. The mid-hill area, with elevations from about 1,200 m to 2,500 m, where the southwest monsoon generally strikes the mountain mass, has the heaviest rainfall, averaging about 1,250-1,500 mm a year. At higher and lower elevations, the rainfall decreases rapidly and the air is correspondingly drier and clearer. The rainfall further decreases rapidly from north to south in the plains, from about 550 mm of annual rainfall in the foothills to only about 100 mm at Mithankot and Sukkur. Below Sukkur, the rainfall increases a little owing to the maritime air, reaching about 200 mm along the sea coast. The mean annual rainfall over the Indus plains is less than 250 mm.

Due to the uneven distribution of precipitation over the basin, the Indus and its tributaries receive most of their flow from the mountains. The flows are subject to extreme variations; the maximum summer discharge is over 100 times the winter minimum. During July and August, all the rivers attain their peaks, discharging a considerable volume of water to the sea (see fig. 2.17).

Fig. 2.17 Average monthly flow of the Indus River and its two largest tributaries

The mean annual run-off of the Indus is 207 x 109 m, with a yearly maximum of 264 x 109 m and minimum of 171 x 109 m. The Indus main stream carries about 110.3 x 109 m per year, while the major tributaries Jhelum, Chenab, Beas, Sutlej, Ravi carry 27.85 x 109 m, 29 x 109 m, 15.65 x 109 m, 16.8 x 109 m, and 7.9 x 109 m respectively. Thus the main stream alone carries a little more than half of the total discharge of the system. When combined with the Jhelum and Chenab, it carries a little more than fourthfifths of the overall total, while the Ravi, Beas, and Sutlej together deliver a little less than one fifth. The run-off coefficients are as high as 58%-82% (ECAFE 1966).

2.3.3 Water-resources development

As rainfall is scarce in the plains, where the cultivable areas lie, agriculture on the Indus plains has to depend almost exclusively on an irrigation system utilizing the river flows.

Many weir and canal systems were built on the Indus and its tributaries from the middle of the nineteenth century onwards, the first of which was the Upper Bari Doab canal, built between 1850 and 1859 to bring water from the Ravi River at Madhopur to the upper half of the doub, or inter-river land, in the vicinity of Lahore. By 1947, when India and Pakistan achieved independence as separate countries, the Indus water system had already been developed to provide irrigation to about 10.9 million ha, but it is remarkable that no storage reservoirs had yet been built in a system serving the world's largest irrigation area. Among the major hydraulic works built before 1947 were the following (see fig. 2.18):

Fig. 2.18 Indus River development

Because the new international boundary cut across the common canal system of Punjab, leaving one part in India and the other in Pakistan, controversy on the use of the canal waters arose soon after the Partition. It took twelve years of patient negotiation before the controversy was settled by the Indus Waters Treaty in 1960. Between 1947 and 1960 intensive river development was carried out, including the following:

The following major works were undertaken through the Indus Basin Development Fund (IBDF) and its successor, the Tarbela Development Fund:

It was originally intended that the IBDF would finance tube-well drainage works to compensate for leakage from the link canal systems, but at the choice of the Pakistan government the tube-well programme was financed by other means and the savings to the IBDF were put towards construction of the Tarbela dam.

2.3.4 Salinity and waterlogging problems

During successive stages of development of the irrigation systems, emphasis was put on maximizing the extent of irrigated land. In the Indus valley, as in all other flat valleys in the world, the natural surface and subsurface drainage is poor. Since there were not enough drainage channels, most of the rainwater and canal seepage percolated down to lower depths. As time passed, the groundwater table got higher and higher by steps, and finally, in the 1950s and 1960s it came close to the ground surface and has thus caused waterlogging in many large areas. Proper aeration of the soil could not take place and the capillary action and evapotranspiration moved salts from the subsurface up to the root zone of the crops and to the land surface. Thus, once-fertile lands so deteriorated that crops could no longer be grown.

In the former Punjab area in Pakistan, 5 million ha have already gone out of cultivation due to salinity caused by waterlogging, 690,000 ha are in an advanced stage of deterioration, and 2 million ha are affected to a lesser degree (fig. 2.16). Since 1954, extensive groundwater and salinity investigations have been undertaken. As a result of these investigations, recommendations were made to install a great number of deep wells to lower the groundwater level, and to use the pumped water for flushing the salts from the ground surface down to the drains provided as well as to the lower layer of soil. Moreover, the pumped water is used to supplement the existing canal supplies for irrigation.

In 1959 the Water and Power Development Authority, established in 1958 to take charge of all water and power development in Pakistan, launched its first reclamation project in Rechna Doab, in the districts of Gujarawala, Sheikhupura, and Lyallpur. The project comprised about 1,800 tube wells in a gross commanded area of 480,000 ha. The average volume of groundwater pumped was about 1.85 x 109 m per year. In 1961 a second project was launched in Chai Doab, including 3,300 tube wells in a gross commanded area of 920,000 ha, with an average pumping volume of about 2.5 x 109 m per year. The Authority has continued this salinity-control and reclamation work to remove the catastrophic threat to the well-being of the people of Pakistan.

The extent of salinity and a schematic diagram of salinity-control land reclamation in the lower Indus valley, using conjunctive aquifer management with surface and subsurface drainage measures, are shown in figs. 2.19A and 2.19B.

Fig. 2.19A Saline groundwater in the Indus valley (Source: Buras 1967)

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