Water Resources in Bahrain

Surface water

Situated in an arid to extremely arid environment, Bahrain’s climate is characterized by high average temperatures, erratic, often scanty rainfall averaging about 80 mm/yr (see Figure 1) and high evapotranspiration rates averaging about 1,850 mm/yr.[1] This results in a high deficit in the water budget, creating impossible conditions for a perennial surface water system to exist.

Groundwater

Bahrain has two groundwater systems: the Dammam aquifer system and the Rus-Umm er Radhuma (Rus-UER) aquifer system. The Dammam aquifer system is recharged by the equivalent aquifer system in eastern Saudi Arabia, and therefore is considered a renewable aquifer system,[2] while the Rus-UER aquifer system occurs in the form of a brackish water lens and is considered non-renewable. Interaction between the two systems occurs in certain parts of Bahrain, as will be illustrated in the following sections.

The Dammam aquifer system is developed in the Dammam formation and represents the only natural, semi-renewable, relatively freshwater source available for Bahrain (Figure cuh1). The system consists of two groundwater zones, the Alat zone (termed ‘A’ aquifer) and the Khobar zone (termed ‘B’ aquifer). The ‘B’ aquifer zone is developed in highly fractured limestones and dolomites and is the principal aquifer in Bahrain, providing most of the groundwater abstraction. The ‘A’ aquifer zone has limited hydraulic properties, and due to its widespread salinization is used at a very local scale by farmers.

The Rus-UER aquifer system, termed the ‘C’ aquifer zone, is developed in the fractured chalky dolomitic limestone of the Rus and the upper parts of the Umm er Radhuma formations. The aquifer occurs in the form of a lens of a finite lateral extent on Bahrain Island, with a salinity range between 8,000 and 15,000 milligrams per litre (mg/L), underlain everywhere with brines of over 100,000 mg/L. Since the Rus-UER aquifer is non-renewable, it is expected that with continued abstraction the reserve of the brackish water zone will be depleted, and its salinity will eventually reach that of seawater or that of the underlying brine zones. Aquifer water is currently used to feed the Ras Abu Jarjur reverse osmosis desalination plant and the industrial sector.

Heavy dependence on groundwater resources, particularly for the development of the agricultural and municipal sectors, has increased groundwater abstraction rates to more than twice the recommended groundwater safe yield (Figure 2). This has resulted in a severe decline in the aquifer water levels, causing all natural springs to cease flowing. [3]indicated that the water levels in the Dammam aquifer have dropped from one to six metres in comparison to the aquifer’s pre-development water levels, with many areas experiencing water levels below sea level. As a result, many agricultural lands were abandoned due to deteriorating groundwater quality, which was partially compensated by treated wastewater.

Figure 2: Production of desalinated water in Bahrain, 1979-2017. Data Source: Electricity and Water Authority.

Non-conventional water resources

Non-conventional water resources in Bahrain consist mainly of desalination and treated municipal wastewater. Industrial wastewater and irrigation drainage water do exist, but their volumes and utilization are relatively minor. The following is a brief summary of desalination and treated wastewater.

Desalination
Bahrain has an established policy of meeting municipal water requirements with desalination plants, and it has a well-developed water utility sector with several large desalination plants that fulfil nearly all of the municipal water requirements. The sector has grown rapidly alongside the kingdom’s social and economic development.

The total desalination capacity reached about 846,000 m³/d or just under 309 million cubic metres per year (MCM/yr) in 2017 (Table 1). Figure 3 shows the desalinated water produced during the period 1979-2017. Currently, about 24.6% of the total capacity is owned and managed/operated by the government while the rest is owned by the private sector, from which the government purchases desalinated water based on long-term agreements.

Table1: Daily production capacity of desalination plants in Bahrain. Data Source: Electricity and Water Authority (EWA).

Note: Al-Dur seawater reverse osmosis plant (third on the list), owned by the EWA, ceased operating as a production facility in 2012 and is excluded from the calculation of the total capacity.

Desalination technologies used are multistage flash distillation (MSF), multiple effect distillation (MED), brackish water reverse osmosis (BWRO) and seawater reverse osmosis (SWRO). The current (2019) desalination technology mix ratio is 33.6% for MED, 30.2% for MSF and 36.1% for RO. In the last five years, the Electricity and Water Authority (EWA) has increased its reliance on RO technology. Subsequently, the ratio of RO technology in the desalination technology mix has increased from 8.3% to 36.1% (2019).

The primary fuel used for desalination is natural gas produced in the kingdom, which is more efficient, less costly and more environmentally neutral than oil. The municipal water authority is planning to increase current desalination capacity by 75% by 2030. The total cost of water supply per cubic metre (i.e. production, conveyance and distribution) is indicated by the water authority at about $2. Bahrain uses a monthly block rate tariff. The subsidies for municipal water supply range from 98% (first block) to 83% (last block).

Treated municipal wastewater reuse
Bahrain has 11 wastewater treatment plants that are owned and operated by the Ministry of Works, Municipalities Affairs and Urban Planning with a total capacity of about 352,770 m³/d (Table 2). The main wastewater treatment facility is the Tubli Water Pollution Control Centre (Tubli WPCC), and is the main plant with tertiary treatment level (another tertiary treated wastewater plant is operated by the private sector and is described below).[4]

Tubli WPCC is the only plant that has a network for transmission of its tertiary treated wastewater for reuse. Other sewage treatment plants (STPs) producing tertiary treated wastewater, such as Ma’ameer and North Sitra, are not connected to a reuse network. Two new STPs are under construction for two newly developed cities: the STP for Madinat Salman in the north-west and the STP for Madinat Khalifa in the south-east.

The actual flow to Tubli WPCC is more than its designed capacity (Table 2), which leads to large carryover volumes of partially treated wastewater to the surrounding environment. An overall decentralization planning policy, and Tubli plant capacity increase and efficiency improvement schemes, are being carried out to solve the problem of hydraulic loading of the plant.

Table 2: Main and minor government-owned wastewater treatment plants in Bahrain. Data Source: Sanitary Engineering Operation and Maintenance Directorate, Ministry of Works, 2017.

In 2015, the amounts of wastewater received at Tubli WPCC were about 116 MCM (318,000 m3/d on average), of which about 35 MCM (96,300 m3/d on average) were tertiary treated. Of this tertiary treated water, about 28.5 MCM (78,100 m3/d on average) were reused for irrigating farms and landscaping, and the remaining 6.7 MCM (18,400 m3/d on average) were used inside the Tubli plant. The rest of the wastewater received, about 74 MCM (203,300 m3/d on average) were treated only to a secondary level and were discharged to the sea in Tubli Bay. Figure 3 illustrates the evolution of these four quantities for the period 2000-2015.

In 2014, a new wastewater treatment plant with a capacity of about 100,000 m³/d (expandable to 160,000 m3/d) of tertiary treatment was commissioned to serve Muharraq Island as part of the wastewater authorities’ decentralization policy.

Figure 3: Amounts of wastewater received in Tubli WPCC, tertiary treated, reused and discharged to the sea, 2000-2015. Data Source: Sanitation Directorate, Ministry of Works.

The project is being overseen by the Muharraq Sewage Treatment Plant Company as part of a 27-year build, own, operate and transfer scheme, the first of its kind in the country. In 2017, the total treated amount at the plant was about 73,700 m3/d (27 MCM/yr). Currently, very limited volumes of this tertiary treated wastewater are reused, totalling about 1,000 m3/d (0.36 MCM/yr), and are delivered to users by tankers. Such large amounts of unused tertiary treated wastewater represent a major lost opportunity under the prevailing water scarcity conditions, especially as an estimated annual amount of about $12.2 billion is paid to treat these waters to a tertiary level. Moreover, with the growing population, it is expected that the annual wastewater generation rates will increase, and the available treated sewage effluent will increase too.

Total water availability and per capita availability

Bahrain has an extremely poor endowment of water resources. It is considered one of the countries with the lowest per capita freshwater availability in the world, a situation that continues to worsen due to population growth. Per capita freshwater availability currently stands at about 70 m³/yr,[5] considerably below the acute water poverty line of 500 m³/yr (Figure 4).[6] However, despite this water scarcity, Bahrain has achieved a very commendable level of water supply services given the rapidly increasing population and urbanization rates, reaching almost 100% of its residents. This achievement has been made possible by the use of a significant share of oil revenues.

Figure 4: Trends in per capita freshwater availability in cubic metres per year, 1940-2015.

Shared Water resources

Groundwater in the Dammam aquifer is renewed on a relatively long-term basis by underflow from the extensive regional Eastern Arabian aquifer (non-renewable), which extends from central Saudi Arabia to eastern Saudi Arabia and Bahrain. Strong cooperation on water issues exists between Bahrain and Saudi Arabia.