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 m³. To this, a further 1.8 x 10⁹ m³ 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 m³ 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 m³ 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 m³ (effective volume, 19.3 x 10⁹ m³).

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 km², of which 233,000 km² is that of the Euphrates, 171,800 km² of the Tigris, and 19,000 km² 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 37°N, 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 km² 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 m³/sec, with the lowest flow of 136 m³/sec in September 1961 and the maximum flood of 6,600 m³/sec in May 1944. The long-term annual average discharge at the Karababa/Ataturk dam site is estimated to be 830 m³/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 m³/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 m³/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 m³ in total at its confluence with the Euphrates, which includes 13.2 x 10⁹ m³ from the Greater Zab, 7.2 x 10⁹ m³ from the Lesser Zab, and 5.7 x 10⁹ m³ 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 m³ 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 m³. 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 m³, was completed on the Lesser Zab River in 1959, while further south, on the Diyala River, the Darbandikhan dam, with 3.25 x 10⁹ m³ 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 m³ 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 m³ 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 m³. To this, a further 1.8 x 10⁹ m³ 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 m³ 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 m³ (effective volume, 19.3 x 10⁹ m³) 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 m³ 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 m³ (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/m³ (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.