|Managing Water for Peace in the Middle East: Alternative Strategies : Solar-Hydro; Hydro-Power; Groundwater-Hydro; Reverse-Osmosis Desalination (UNU, 1995, 309 p.)|
|3. Hydro-powered reverse-osmosis desalination in water-resources development in Kuwait|
The climate of Kuwait is characterized by an extremely hot summer, from June to September, with occasional periods of extreme humidity and an average maximum daily temperature of 45°C. The winter season is mild to cool, with a minimum temperature of-1°C.
The average annual rainfall is about 115 mm, with a minimum of 30 mm in 1960 and a maximum of 360 mm in 1954. The rainfall records at four gauging stations-the International Airport, Ahmadi, Umm al-Aish, and Showaikh-since 1952 are shown in fig. 3.2. Histograms of monthly rainfall at the International Airport and Shuwaikh are shown in fig. 3.3, which indicate that 75% of the rainfall occurs in the four months from November to February. There is also spatial variation of rainfall, such as 136.2 mm at Ahmadi station in 1972 while it was only 18.1 mm at Alomaria.
The mean annual potential evaporation values as measured by class A-pan and Piche evaporimeters were 3,460 mm (1962-1977) and 5,460 mm (19571977) respectively. The theoretical annual average potential evaporation as estimated by the Penman method was approximately 2,630 mm (1957-1977). The monthly average potential evaporation and rainfall at Kuwait International Airport is shown in fig. 3.4.
Fig. 3.2 Rainfall variation, 1953-1986: Kuwait International Airport, Ahmadi, Umn al-Aish, Shuwaikh (Source: Abusada 1988)
Fig. 3.3 Monthly rainfall, Kuwait International Air. port and Shuwaikh (Source: Abusada 1988)
Kuwait is a hyper-arid state without rivers or fresh-water aquifers. Nonconventional water resources, including brackish groundwater, seawater desalination, and reclamation of treated waste water are the main current sources of water supply, of which the quality is as saline as 1,000-45,000 mg of total dissolved solids (TDS) per litre:
The WHO standard for the maximum permissible level for drinking water is 1,000 mg of TDS per litre.
Fig. 3.4 Monthly avenge potential evaporation and rainfall at Kuwait International Airport (Source: busada 1988)
3.2.1 Surface water
The prevailing hyper-arid climate of Kuwait is not favourable to the existence of any river systems in the country. There are no rivers or lakes, but small-scale wadis are developed in the shallow depressions in the desert terrain. Surface run-off sometimes occurs in the large wadi depressions during the rainy season from November to April. There is no permanent stream-gauging station, but flash floods are reported to last for only a few hours to several days. Due to the extremely high evaporation losses and the high deficit in soil moisture, only a small percentage of the precipitation infiltrates into the groundwater. The run-off ratio must be extremely small.
The average annual rainfall within Kuwait is estimated to be 1,780 million m³, assuming a mean annual rainfall of 100 mm. However, with such high evaporation losses, the net annual run-off is estimated to be merely 17.8 million m³, assuming a run-off ratio of 1%.
Thick geological sequences are of sedimentary origin from Palaeocene to Recent, in two groups, known as Hasa and Kuwait. The Hasa group, which consists of limestone, dolomite, anhydrite, and clays, comprises three formation units, known as Umm el-Radhuma in the Palaeocene to Middle Eocene, Rus in the Lower Eocene, and Damman in the Middle Eocene. The Kuwait group, which consists of fluviatile sediments of sand and gravel, calcareous sand and sandstone with some clays, gypsums, limestones, and marls, comprises three formation units, known as Ghar in the Miocene, Fars in the Pliocene, and Dibdibba in the Pleistocene (fig. 3.5).
Two economic aquifers are found in the Damman formation in the Hasa group and the Dibdibba formation in the Kuwait group.
Fig. 3.5 Schematic geological profile of Kuwait
Fig. 3.6 Salinity (TDS) contour map of the Darnman aquifer in Kuwait (Source: Abusada 1988)
DAMMAN LIMESTONE AQUIFER. The Damman aquifer of the Middle Eocene, which consists of carbonate rocks and extends all over the country, has a thickness varying from about 150 m in the south-west to about 275 m in the north.
The dissolution of gypsum and anhydrite in the Kuwait group, Damman formation, and Rus anhydrite formation is an important factor conditioning the chemical quality of groundwater in Kuwait. The total dissolved solids of groundwater in the Damman limestone aquifer vary from 2,500 mg/l, in the extreme south-west to about 200,000 mg/l in the north-east (fig. 3.6).
Groundwater isotope analysis of 14C in the Damman aquifer has been performed by taking water samples from 13 wells in southwestern Kuwait. From the absence or zero concentration of 14C the age of the groundwater in the Damman aquifer is estimated to be more than 400,000 years, while the 14C concentration in the Kuwait group groundwater indicates an age of 14,000-22,000 years (Abusada 1988).
Owing to the nature of limestone geology, the permeability of the Damman limestone aquifer varies considerably. The aquifer parameters vary from 27 to 7,100 m²/day transmissivity and 3.4-8.9 x 10 -4 storage coefficient, based on results obtained from 38 testing sites in south-western and southern Kuwait (Abusada 1988).
No natural groundwater recharge from rainwater is likely in the confined Damman limestone aquifer, although there is some lateral inflow or recharge through the Saudi border, which is preliminarily estimated to be 8.3-24.9 million m³ per year (Abusada 1988).
DIBDIBBA AQUIFER. The Dibdibba aquifer, which is composed of unconsolidated sands and gravels, is generally a water-table aquifer with fresh to brackish groundwater.
Most of the groundwater recharge of the Kuwait group is dependent on upward leakage from the underlying confined Damman limestone aquifer. The quality of the groundwater is generally similar to that of the Damman aquifer. The total dissolved solids of the groundwater in the Kuwait group increase generally from about 3,000 mg/l in the south-west to about 130,000 mall in the north-east over a distance of about 150 km. Some lenses of fresh water with TDS ranging between 800 and 1,200 mg/l, are perched on the brackishgroundwater body in the Rawdatain and Um al-Aish wellfields in northern Kuwait, which are recharged by infiltration through the wadi beds during occasional flash floods in the wadi depressions (fig. 3.1).
The piezometric level in the Kuwait group varies from about 90 m in the south-west to zero along the coast. The groundwater flows generally northeastwards.
Seawater is an unlimited water source for Kuwait, which has a long coastline along the Arabian Gulf, which covers an area of 3,683 million km² and holds 10.07 x 10 12 m³ of water (Korzun et al. 1976)
The high mineral content of water from the Arabian Gulf requires special attention for the control of salt deposition in plants located there. The total dissolved solids of the feed water from Kuwait bay at Doha average 44,885 mg/l, (Al-Zubaidj 1989), which is as much as 1.3 times that of other standard seawaters, such as 33,600 mall in the Pacific Ocean and 36,000 mg/l, in the Atlantic (Howe 1962). Seawater has been the major source of the fresh-water supply in Kuwait since the 1960s and is likely to continue to be the key source for developing water resources in Kuwait in the twenty-first century.
3.2.4 Treated sewage effluents
Marginal waters in the artificial category are composed primarily of municipal waste water and urban storm drainage water. The potential reclaimed sewage effluents in Kuwait city were estimated to be 190 million m³ per year in 1988, assuming a water supply of 293 million m³ per year with a 65% rate of return flow. The actual amount of reuse of sewage effluents in 1988 was 97 million m³ per year, which was one third of the volume of water supplied. The potential for water reuse will increase, corresponding to the increasing water use in the future.