Groundwater resources in the UAE
Groundwater exists naturally in the usable or extractable from beneath the earth’s surface. It occupies soil pore spaces and the fractures of rock formations underground that can connect to other underground water bodies like aquifers.
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Amount of water
The groundwater in UAE meets the needs of 51% of users in terms of quantity mainly for irrigation. As the main natural resources, its distribution is scarce in the southern and northern parts of the country. The estimated volume of groundwater is 640 BCM, which is very large. Unfortunately, only 20 BCM of the available water is considered fresh. Based on current demand, the UAE total annual water demand will double from 4.4 BCM in 2008 to 8.8 BCM in 2030. Demand for water will mainly be in urban areas. These uses include industrial, commercial, public facilities, and institutions. The current demand for forestry or agriculture will decrease in the same period or shift to other sources of water other than groundwater (Al Mulla 2011).
Groundwater existed as the main source of water for all users in the country until rapid demand forced authorities to develop alternative sources of water. Also, the rapid expansion of development and urbanization are factors to look out for when evaluating water quality. The two factors have led to the over-abstraction of groundwater to meet the larger needs for agriculture. This has resulted in a sharp drop in water levels in the fresh groundwater region. Moreover, there is a constant salt-water intrusion from the sea.
This mainly happens in the coastal regions of the UAE. It arises from the lateral movement of saline water. The close sabkha-dominated areas are a source of the intrusion. Moreover, the upwelling of salty water from low stratigraphic units is another major source of the intrusion. The low-quality water enters the shallow aquifers that are sources of groundwater. On the other hand, increased agricultural production has meant an increase in chemical fertilizers that have caused a rise in nitrate concentrations in some areas where groundwater is available.
Much of the UAE experiences high temperatures that reach over 40 degrees centigrade in summer. The rate of evaporation is very high at about 8.2mm and the annual mean rainfall is about 120 mm. These factors affect the potential of near-surface groundwater to exist and renew based on the rate of extraction for consumption. The main recharge for groundwater is rainfall, which goes off as runoff and sips into the group to recover the groundwater amounts. The total renewable freshwater resource for the UAE is estimated as less than 150 MCM/Year and this includes the groundwater sources as well as the surface water sources.
On the other hand, demand for water has been increasing with the largest consumers being forestry and agriculture as users of groundwater while amenity and domestic mostly used other sources of water. The flashfloods dams constructed around the UAE to collect surface water are also major sources of groundwater recharge. Climate change is also increasing the vulnerability of water scarcity in the UAE. The effect can be reduced when water demand management changes to be more efficient (Al Mulla 2011).
The protection of groundwater starts with the assessment of the quality of water available and determining the major risks facing the supply of fresh groundwater. Groundwater bodies can then be classified as good or poor based on their quality and size before measures are taken to protect the water. The abstraction of groundwater is the main cause of pollution as it causes saline intrusion. The salinity is increased in a given area when there is the use of water for irrigation. Most irrigated lands are waterlogged and saline and the surface waters get underground to pollute fresh sources.
Therefore, the first and most significant action against the destruction of groundwater sources is to have limits on ground flooding with saline irrigation water. In this case, the area may have to place a ban on irrigation types to prevent such flooding that is an inefficient way of using water and is a major risk of salinizing the available groundwater. In the case of the UAE, the biggest threat is encroachment by seawater. Some aquifers may also have a very slow flow rate and when they do not receive enough recharge of freshwater, they deteriorate in their water quality. Another source of water deterioration would be from mining activities that have mine drainage and tip leaching. For the UAE, mining causes can be the infiltration of discard oilfield brines.
There is a relation between surface water and groundwater. Surface water is the source of groundwater and plays a major role in groundwater renewal. Surface water sips into the soil and rocks beneath it to become groundwater. On the other hand, groundwater reappears as surface water what there is a sudden change in altitude to create springs and surface water bodies.
According to Demirak et al. (2006), heavy metals come from a variety of natural and anthropogenic sources. The combustion of coal is one of the most important sources of anthropogenic emission of trace elements including several metals. The metals then distribute in sediments adjacent to the settlement areas. The heavy metal pollution can be manmade due to the establishment of coal-burning plants and it can also be natural in areas of fluvial conditions, metal pollution happens due to direct atmospheric deposition.
Heavy metals pollute water to make it unsuitable for human consumption and animal consumption. The study by Demirak et al (2006) showed that the presence of a coal power plant known to be a major source of heavy metal deposits in soil sediments. However, this is not a guarantee that downstream water will be polluted to the extent that maximum safety levels of the water are detected upon testing. However, there is a need for caution as pollution through heavy metals is accumulative.
Heavy metal water pollution in many parts of the world arises from industrial waste coming from mining, metallurgy, foundries and similar industries. When human and animal bodies absorb heavy metals they experience severe damage in their vital organs and can lead to failure of the organs. There are ions of heavy metals in consumable water piped or transports many miles from the incident of pollution. Therefore, heavy metal water pollution is a threat to many more people and environments other than the locality adjacent to the main source of pollution (Vila et al. 2011).
The pyrite mine-reservoir accident in Aznalcóllar, Spain in 1998 was a national environmental catastrophe that highlighted the potential scale of heavy metal hazards to the environment. After the incident, there were massive clean-up initiatives that include mechanical removal of toxic sludge and surface soil. The accident jeopardized the quality of groundwater in the area and adjacent areas that rely on Aznalcóllar for the replenishment of the ground or surface water supply. The accident was constrained by the application of soil amendments aimed at preventing the dispersion of the contaminants.
Nevertheless, the area remained contaminated. Also, the activities of cleaning up that included the removal of sludge ended up burying more sludge. The pollution damage than occurred when the aerobically enhanced pyrite oxidation in the sludge-contaminated soil reacted with the metallic and metalloid elements present through the acidification process to result in increased risks of contamination (Vázquez et al. 2011). After the reactions, much of the soil and sludge were contaminated and it had become very acidic.
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While in the soil, the heavy metal elements are influenced by factors such as soil pH, the presence of organic matter, the redox potential of the soil and the temperature. When there are favorable conditions, physical, chemical and biological processes act without intervention of humans to reduce mass, toxicity, and mobility or the volume and concentration of contaminants like heavy metals from groundwater and the soil. In the case of the Aznalcóllar soil contamination incident, there have been limited studies to evaluate the effect of years of attenuation and confirm whether the groundwater was still susceptible to pollution.
After the accident, seasonal rainfalls on the soil affected soil pyrite oxidation and caused a significant decrease in soil pH after it had initially increased due to the accident. The rains also caused leaching of salts especially in the period from the year 2003 to 2006. Another feature that contributed to reduced toxicity was the accelerated growth of wild plants and weed growth. The reclamation of the land through the natural process was fast because the initial topsoil had been mechanically removed together with the sludge. However, there was the continued release of Fe oxides from pyrite due to oxidation and succeeding perspiration.
The area also experienced a vertical distribution of elements across the soil profile leading to increased soil acidity and increased risk of groundwater contamination in the adjacent areas. Overall, most water pollution risks of heavy metals come from manmade activities or accidents like the mine disaster in Spain in 1998. The damage starts with the soil which then affects surface waters when there are runoffs or groundwater after subsequent perspiration activity.
Water quality associates with the balance of chemical, biological, physical, and radiological characteristics of water when analyzed. Water from different sources has different quality attributes that can be analyzed by looking at the color, conductivity, dissolved oxygen, electrical conductivity, pH, hardness, salinity, suspended sediment and turbidity. The remark on water quality and suitability will also depend on the intended usage of the water.
Water-related diseases are diseases that arise when there are water problems such as contamination or shortage. On the other hand, waterborne diseases are a type of water-related diseases arising when the transmission of the disease occurs through drinking contaminated water. The contamination is by pathogens that are transmitted from excreta to water through human activity (Gleick & Cain 2004). Waterborne diseases include most diarrheal disease that is caused by viruses, parasites and bacteria, and typhoid. Thirty other parasites that are known to affect the human intensities upon taking such water are also contaminants. Other forms of water-related diseases include water-washed diseases and water-based diseases.
The illnesses occur when there is limited water that could be used to wash and sustain personal hygiene. Thus, individuals become infected with diseases. The water-based diseases occur when hosts whose habitat is water or whose survival need is water pass on diseases to humans. They can be ingested or they can be exposed to the skin. Upon doing so, they cause diseases in humans. Examples of illnesses arising in this manner are schistosomiasis and dracunculiasis, which are quite deadly going by the fact that they have victimized more than 200 million people globally (Gleick & Cain 2004).
When living in a rural community where water safety is a priority, the first thing will be to check that there is no contamination of the current supply of drinking water. Dams and other water sources would be fenced off to avoid human activity that can introduce contamination. There will be filtering and boiling of water before drinking as a way of killing all organisms that might be responsible for causing infections. There will also be sensitization programs for the residents of the rural area about maintain their hygiene as individuals. The campaigns will continue to their work or home to reduce the chances of contamination and the spread of water-related diseases.
Sludge comes as a byproduct of water treatment and it can be on-site or off-site. The sludge contains solids. They would have been removed from the water during treatment. Thus, the sludge is often organic due to soluble organic substances. They convert to bacterial cells after extraction from water. Sludge varies widely in its characteristics because it comes from many sources. It can be from fresh fecal material. This would have been collected from bucket latrines. After that, the sludge can undergo bacterial decomposition for more than a year in a pit latrine. Overall, sludge from different sources will have pathogens that can cause diseases. Therefore, it should be handled with care. In addition to pathogens, sludge may contain heavy metals and other deadly pollutants that risk being reintroduced to water meant for human and animal use.
The level of treatment needed for sludge before releasing it to the environment differs according to the potential contamination contained within it. Fecal sludge is rich in nutrients. The main ones are nitrogen and phosphorus. Therefore, it has potential nutritional benefits to plants when used as fertilizer. Such sludge also has carbon that stabilizes and becomes a soil conditioner, which advances soil texture and provides a proper structure for roots. Treatment of sludge starts with stabilization from a point of high biochemical oxygen demand. The stabilization reduces this demand. Sludge can be stabilized aerobically. This would happen in aeration tanks similar to an activated sludge procedure. In the process, thickening and dewatering happen to gain enough solids content and convert sludge into usable organic matter. Sawdust may also be used. Also, the sludge can be processed through composting or aerobic digestion to make methane and carbon dioxide gas as biogas.
Composting can be simple. It may include the use of windows, which help in providing oxygen to the bacteria responsible for decomposition. As a result, the overall rate of decomposition increases. Therefore, heat insulation during the process is also necessary. After composting, the sludge is ready for use as organic fertilizer or buried (UNEP 2015).
Water sustainability indicators
Sustainability aims to use resources in a way that does not deplete their sources and water sustainability seeks to achieve the same through careful management of water sources and improvement of processes that lead to the regeneration of water supply. Water sustainability indices are used to evaluate the extent of sustainability of practices used in managing water. The water sustainability definition comes from the existing definitions of sustainable development principles that various institutions such as the United Nations have proposed. Water is considered a resource and its sustainability are achieved by having water resource systems designed and management do fully contribute to the objectives of the society. The condition has to be relevant now and in the future while the integrity of ecological, environmental and hydrological properties is maintained.
Indicators are measures of facts or conditions that can be qualitative or quantitative. Regular observation of indicators can provide data for analysis for a particular period. When indicators are grouped, they result in a component. Also, indicators can have sub-indicators. When several indicators are put together, they make up an index or composite indicator. Water sustainability indicators are selected based on their sensitivity to change in time, change across space and their predictive or anticipatory nature. They have to be unbiased, integrative, offer appropriate data transformation and have reference or threshold values available. Formulas for water sustainability vary but use key methods such as categorical scaling and continuous re-scaling. They can also use distance to a reference (Juwana, Muttil & Perera 2012). Indicators are assigned weights that will be used to develop the index and determine water sustainability as a measure of its replenishment risk over time.
Al Mulla, MM 2011, UAE state of the water report 2nd Arab Water Forum, Web.
Demirak, A, Yilmaz, F, Tuna, AL & Ozdemir, N 2006, ‘Heavy metals in water, sediment and tissues of Leuciscus cephalus from a stream in southwestern Turkey’, Chemosphere, pp. 1451-1458.
Gleick, PH & Cain, NL 2004, The world’s water 2004-2005: The biennial report on freshwater resources, Island Press, Washington, DC.
Juwana, I, Muttil, N & Perera, BJC 2012, ‘Indicator-based water sustainability assessment — A review’, Science of the Total Environment, vol 438, pp. 357-371.
UNEP 2015, Sludge treatment, reuse and disposal, Web.
Vázquez, S, Hevia, A, Moreno, E, Esteban, E, Peñalosa, JM & Carpena, RO 2011, ‘Natural attenuation of residual heavy metal contamination in soils affected by the Aznalcóllar mine spill, SW Spain’, Journal of Environmental Management, vol 92, no. 8, pp. 2069-2075.
Vila, M, Sánchez-Salcedo, S, Cicuéndez, M, Izquierdo-Barba, I & Vallet-Regí, M 2011, ‘Novel biopolymer-coated hydroxyapatite foams for removing heavy-metals from polluted water’, Journal of Hazardous Materials, vol 192, no. 1, pp. 71-77.