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The prevailing hyper-arid climate of Kuwait is not favourable to the existence of any river systems in the country. There are no permanent rivers or lakes, but small wadis develop in the shallow depressions in the desert terrain. Surface runoff sometimes occurs in the large wadi depressions during the rainy season. Flash floods are reported to last from 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 supply. Internal renewable groundwater sources are negligible. Groundwater inflow has been estimated at about 20 million m3/year through lateral underflow from Saudi Arabia (Table 2).
Thick geological sequences are of sedimentary origin from the 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 er Radhuma in the Palaeocene to the Middle Eocene, Rus in the Lower Eocene, and Damman in the Middle Eocene. The Kuwait group, which consists of fluvial sediments of sand and gravel, calcareous sand and sandstone with some clays, gypsums, limestone, and marls, comprises three formation units, known as Ghar in the Miocene, Fars in the Pliocene, and Dibdibba in the Pleistocene (UNU, 1995).
Groundwater can be divided into the following three categories according to its salt content (Public Authority of Agriculture Affairs and Fish Resources, 2006):
- Fresh groundwater: its content of soluble salt is less than 1 000 mg/l and such water is not used for agriculture but is considered as a strategic freshwater reservoir for drinking water purposes. It is mostly available in the two fields of Rawdatian and Umm Al Eish. These freshwater lenses are formed due to a combination of unique conditions that include high intensity rainfall of short duration, and a geomorphology and lithology that enable rapid infiltration to the underlying groundwater. From historical pumping and water quality variation data acquired between 1963 and 1977, the sustainable extraction rate for Rawdatain and Umm Al Eish, which would avoid the upcoming of deeper saline water, is estimated to be 5 500 and 3 500 m3/day respectively (Kwarteng et al, 2000).
- Brackish groundwater: its soluble salt content is from 1 000 to 7 000 mg/l and is used for agricultural and domestic purposes and as drinking water for cattle. This water is produced from the Al Shaya, Al Qadeer, Al Solaybeia, Al Wafra and Al Abdali fields. The production capacity of these fields is around 545 000 m3/day.
- Saline groundwater: the soluble salt content in this water is between 7 000 to 20 000 mg/l and it is therefore not appropriate for agricultural or domestic use.
In general groundwater quality and quantity are deteriorating due to the continuous pumping of water. In Al Wafra in the south, 50 percent of the wells pumped water with a salinity level higher than 7 500 ppm in 1989, reaching 75 percent and 85 percent in the years 1997 and 2002 respectively. In Al Abdali in the north, these figures were estimated at 55, 75 and 90 percent respectively.
The first plant for desalinating sea water was established at Al Ahmadi port in 1951, with a capacity of 364 m3/day. The production capacity increased over the years until it reached 1.1 million m3/day, while maximum consumption reached 0.9 million m3/day in the summer of 1995 (PAAFR, 2006). In 2002 the annual quantity of desalinated water produced was 420 million m3 (FAO, 2005). The problem with seawater distillation is the high cost of the multi-stage flash (MSF) evaporation process. The cost of the thermal process is largely dependent on the rate of energy (fuel) consumption for operating the system, which can account for as much as about 50 percent of the water unit cost, thus being sensitive to the unstable world market price of crude oil (UNU, 1995).
Over 90 percent of the population is connected to a central sewerage system. This offers an important potential for treated wastewater reuse that can contribute to alleviating the water shortage problem. However, various conditions affect the quality and quantity of sanitary sewage from the time it enters the local collector sewers until it is converted to sludge and treated sewage effluent at the sewage treatment plants. Qualitative and quantitative monitoring of the system and of the effluent from the time it leaves treatment plants to the end use for irrigation is essential to prevent the potential hazards associated with wastewater reuse. The sewerage system consists of an assemblage network that is based on gravity and which collects wastewater and transfers it to 60 pump stations (17 main and 43 secondary) from which it is pumped into pipelines all the way to wastewater treatment plants (WWTP) where it is treated. Total length of pipelines is 650 km. The sewerage system collects over 90 percent of the raw domestic and some industrial wastewater (220 million m3/yr), in addition to part of the storm water runoff in the residential areas which are connected to the sewerage system. The main WWTP, including those in operation, planning and implementation, are shown in Table 3 where the current treated volumes are indicated. Wastewater treatment has two main purposes: i) to protect public health and the environment; ii) to use treated wastewater for irrigation to compensate for the water deficit. In 2002 the wastewater treated represented 152 million m3 of which 78 million m3 was reused, which means an increase of 48 and 50 percent respectively compared to 1994. In 2005 the total amount of treated sewage water was estimated at 250 million m3/year (FAO, 2005). Treatment plants are gradually being upgraded to advanced levels of treatment with the first plant (Al Solaybeia) planned to begin operating by the end of 2004 using a very advanced level of treatment, the RO-Plant (FAO, 2005).