4.2 The water resources of Jordan

Hydro-meteorologically, Jordan is semi-arid to arid, with relatively abundant water resources as compared with other states in the Middle East such as Kuwait. About 80% of its territory is steppe and desert where water is only minimally available. Jordan, however, has various sources of water, such as rivers and streams, springs, wadi flash floods, renewable and non-renewable groundwater, and reclamation of treated sewage effluents.

4.2.1 Water-resources potential

Water resources in Jordan depend mainly on precipitation within the country, except for the Yarmouk River, whose flow is mainly fed by rainfall on Syrian territory. Average rainfall ranges from 600 mm per year in the northern uplands to less than 500 mm per year in the southern and eastern desert areas. The rainfall occurs between October and May, and is at its height between December and March, when over 80 % of the annual rainfall occurs.

The average annual volume of rainfall within Jordan has been estimated to be 8.5 x 10⁹ m³. However, with high evaporation losses, the average net annual yield is only about 1.12 x 10⁹ m³ (13%), with 875 million m³ (10%) in the form of surface water and 242 million m³ (3%) in groundwater (Huang and Banerjee 1984). About two-thirds of Jordan's potential usable water resources is surface water. About 400 million m³ per year of the surface flow, which is 46 % of the total runoff, forms the discharge in the Yarmouk River. Sustained-yield and/or renewable groundwater resources are preliminarily estimated at 3% of the annual rainfall; their recharge is mostly dependent on rainfall on the western highlands. In addition, it is estimated that over 11 x 10⁹ m³ of stored fresh groundwater exists within the state, but this is mostly non-renewable groundwater which may offer opportunities for short-term and emergency uses.

4.2.2 Surface water resources

Surface water resources, which constitute two-thirds of Jordan's potential usable water resources, are at present used exclusively for agriculture, except for spring water, which is sometimes collected for municipal use. Most of the municipal water supply systems and industries in Jordan at present depend on groundwater and springs. Although surface water resources exist on the northern border such as in the Yarmouk River, in the Jordan valley, and in some of the wadis flowing into the Jordan River, exploitation of surface water for municipal and industrial water supply has not so far occurred to any great extent because of sporadic flow patterns, priority use for irrigation, relatively low elevation, and the long distances to population centres.

River flows are generally of a flash-flood nature, with large seasonal and annual variation. Annual base flows, moreover, whose volume is estimated at 540 million m³, vary by at least 15%-20%, depending on rainfall patterns with a return period of five years (Huang and Banerjee 1984). The base flow of 150 million m³ per year in the Yarmouk River has been developed by the East Ghor Main Canal (EGMC) irrigation project since 1965. Corresponding to the rapid increase in water demand in the metropolitan area, 45 million m³ of canal water has been diverted from the EGMC to Amman for municipal and industrial use by constructing a treatment plant and pipeline with a total difference (pumping) head of 1,300 m.

Since the beginning of the 1960s, a number of storage dams have been constructed that together hold an estimated 452 million m³ of water. The AlWuheda dam, which is being built on the Yarmouk River near the Syrian border to store 225 million m³, will supply irrigation water for downstream in the Jordan valley and will generate electric power. Syria will use part of the water and 75% of the total hydroelectric power (World Bank 1988).

4.2.3 Groundwater resources

Major potential aquifers are found in the pervious sequences in the basalt system of the Pleistocene, the Rijam (B4) formation of the Lower Tertiary, the Amman-Wadi Sir (B2/A7) formation of the Upper to Middle Cretaceous, the lower Ajlun (A1-6) formation of the Middle Cretaceous, the KurnubZarqa formations of the Lower Cretaceous, and the Disi formations of the Palaeozoic age.

The shallow aquifer systems of basalt-Rijam (B4) form a locally important aquifer in the central part of the Jafr and Al-Azraq-Wadi as-Sirhan basins. Groundwater irrigation has been practiced in and around the town of Jafr since the 1970s, but the underlying aquifer B4 has been contaminated by stages by irrigation return flows, increasing salinity (TDS) from 500 mg/l to 4,000 mg/l, during the ten years of operation. The sustained yield is estimated to be less than 2 million m³ per year, because of the limited groundwater recharge through the wadi beds during the occasional flash floods. The basalt-Rijam system in the Azraq basin has been intensively exploited for the purpose of Amman municipal water supply. Annual abstraction from the Azraq wellfield reached 15.6 million m³ in 1985, which exceeded the safe yield, lowering the piezometric head and increasing water salinity. Groundwater in the Sirhan basin, of which the recharge mechanism is the same as that of the Jafr basin, is untapped.

The most important aquifer system is the Amman-Wadi Sir (B2/ A7), which consists of limestone, silicified limestone, chert, sand limestone, and sandstone of Upper to Middle Cretaceous age. This system extends throughout the entire country with thicknesses of about 100350 m. The depth of the groundwater table below ground level generally ranges from 50 to 250 m in the uplands. Good groundwater recharge occurs from the western highlands, where the annual rainfall ranges from 200 to 600 mm. To the east, the aquifer is confined by thick marl such as the Muwwaqar (B3) formation, and water salinity is high. This economic aquifer system, B2/A7, has been excessively exploited in the northern part of the country, lowering the piezometric levels and causing deterioration in water quality. In the southern part of the country such as the Mujib basin, the Upper Hasa basin, and the Jafr basin, the B2/A7 aquifer is the most important economic aquifer, of which the quality is as good as less than 500 mg of TDS per litre. The groundwater is being pumped for M&I water supply from the wellfields of Qastal, Siwaqa, Qatrana, Sultani, Karak, Shoubak, and Hasa.

An intermediate aquifer system is the lower Ajlun (A1-6), which consists of alternating limestone, marl, shale, chert, and sandstone of Middle Cretaceous age. This system is underlain by the Amman-Wadi Sir (B2/A7) formation, which is mostly confined by its relatively impervious layer of marl and shale in the A5/6A or upper unit of A1-6. The lower Ajlun formation extends throughout the country with variable thickness and litho-facies. Southwards, aquifers in the lower Ajlun formation become more sandy, and salinity becomes as little as 350 mg of TDS per litre. The aquifer system is mostly untapped, however, because of its complicated hydrogeology and deep formation.

Deep sandstone aquifers are the Kurnub/Zarqa of Lower Cretaceous age and the Disi of Palaeozoic age, which are unconformably separated by a less permeable layer of sandstone, siltstone, and shale. The Kurnub formation intercalates frequent argillaceous layers in the south, while the Disi is composed of massive and rather homogeneous arenaceous layers. Groundwater in these aquifers is mostly non-renewable because of limited groundwater recharge through small outcrop areas. The quality of the groundwater in the Kurnub-Zarqa system varies from fresh to brackish. Excellent quality with low salinity, however, is found in the Disi aquifer in the southern part of the country, which has been exploited for the water supply of Aqaba and local experimental irrigation. The development potential of Disi groundwater has been estimated to be about 100-200 million m³ per year for a period of over 50-100 years. The aquifer complex, however, forms a huge groundwater reservoir extending under the whole of the country. This groundwater storage offers opportunity for short-term and emergency uses.

Groundwater is presently used for municipal, industrial, and agricultural purposes. In the northern uplands, which include the heavily populated Greater Amman and Irbid areas, groundwater in the Amman-Wadi Sir aquifer has been over-exploited in the 1980s. Significant irrigation water use is also found in the Zarqa River basin, where about 70% of the water is from groundwater. Abstraction in the northern uplands is estimated at about 120 million m³ per year against an estimated sustainable yield of 90 million m³ per year.

It is said that 96% of the kingdom's population is now supplied with drinking water from springs and groundwater wells. A series of water supply schemes have been carried out, including the following groundwater projects-the Wadi Arab scheme west of Irbid (20 million m³ per year), the Azraq project (15 million m³), the Amman-Zarqa project, (14 million m³), the Qatrana-SiwaqaQastal project (9 million m³), the Sultani project near Karak (3.5 million m³), the Shoubak project (1.5 million m³), and the Disi project (17 million m³)-and the Deir Alla-EGMC pipeline project (45 million m³) (World Bank 1988). The Mukheiba wellfield (26 million m³ per year), which was developed for irrigation water supply downstream of the Yarmouk/Ghor, will be diverted to upland water supply by taking advantage of the difference in the water head of about 200 m between the artesian wellfield and the Ghor.

4.2.4 Treated sewage effluents

Significant work on sewerage has taken place during the last decade, and about 40% of the urban population (25 % of the country's population) is now being served. In many urban areas, however, household cesspits and septic tanks are still commonly used, with liquid effluents discharging into the soil via open-joint pipes or openings in pit wells. This return flow mixes with groundwater recharge from rainfall, which is reused for water supplies, and incremental increases in mineral content and high nitrate concentrations have been monitored in the groundwater under some densely populated areas.

Groundwater in the Wadi Arab wellfield, which draws from the AmmanWadi Sir aquifer (B2/A7), was contaminated by direct infiltration from sewage effluents in 1988 through an outcrop of B2/A7 in the upstream area. Drainage of sewage effluents from Irbid city was diverted to the north to protect the quality of groundwater in and around the outcrop area of the B2/A7. Direct recharge of sewage effluents into the limestone aquifers is not planned.

The Zarqa River, which runs through the heavily populated cities of Amman, Zarqa, and Ruseifa, collects the return flows of sewage efffluents. The sewage effluents mix with surface water in the river system and are stored in the reservoir of King Talal dam, which is used exclusively for irrigation water supply in the Jordan valley downstream and not for municipal water supply.