The role of aquifer storage and recovery (ASR) in sustainbility
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Kuwait is an arid country situated at the head of the Arabian Gulf and its water resources can be classified into three significant types: (1) natural (groundwater) and (2) artificial (desalinated sea water and treated wastewater). In the absence of surface water bodies, groundwater constitutes the most important natural water resource in Kuwait with TDS [less than or equal to]10000 mg/L in central and south Kuwait. Only in the north can one find fresh water lenses. Brackish groundwater are used for irrigation, landscaping, construction work, non-potable use in households and mixing with desalinated water up to 10%, to make it potable. The occurrence of usable groundwater is limited to the Kuwait Group and Dammam Formation. Due to over-pumping of groundwater over the last few years, the levels and quality of groundwater are deteriorating. Kuwait is described as the poorest country in terms of water availability (UN World Water-2003). The current rates of water consumption are very high, with 459.6 L/C/d and almost 91 L/C/d for fresh and brackish water, respectively. The water budget of the water resources, represented as percentages is 59% from desalination sea water plants, 32% from groundwater with the possibility to increase the use of this resource and 9% from waste water reuse plants. Although Kuwait does not have any surface water, but it depends on technology to produce water recourses to meet the demand. The best solution for solve the issues of declining water levels and increasing salinity is artificial recharge. Artificial recharge has been applied in Kuwait in different groundwater fields since the 1980s. In addition, the available surface storage capacity of 11.7 Mm³ freshwater is sufficient to meet demand for about 7 days. So, Aquifer storage and recovery (ASR) can be used to store the water in aquifers instead of surface storage. ASR entails storing water in aquifers during wet times and recovering the water from the same well during drought times. Surface storage needs construction resources and vast land. In contrast, storing water in aquifer storage does not need that and it can decrease salinity and keep the water table constant. The water availability for artificial recharge can come from desalination and wastewater plant. The capacity and production of desalination plants are 1.425Mm³/day (525.125Mm³/yr) and 1.31Mm³/day (478.15 Mm³/yr), respectively from 5 stations. The excess capacity is 115000 m³ per day and could reach 290000 m³ per day in the winter season. Wastewater treatment plants produce from 3 plants around 0.337 Mm³/day (123.342 Mm³/yr) and the newest plant (operating by RO system) produces 0.32 Mm³/day (117.12 Mm³/yr) and will reach 0.643 Mm³/day (235.338 Mm³/yr) in 2015. The water produced from wastewater treatment plants has good quality and can be used for irrigation, greening enhancement, landscaping, recreation (artificial river and lakes) and artificial recharge. Also, using water treated for artificial recharge will improve the quality of injected water that has been successfully treated with soil aquifer treatment technology. Groundwater pumping is 200 Mm³ annually and is likely to reach 280 Mm³ in the future. This research will explore and create a database for water resource by GIS software using its tool to select and display suitable areas for ASR operation. Artificial recharge in Kuwait has used the concept of injection and recovery of water in one cycle, while here we will apply the multi-cycle concept to avoid increasing the piezometric head and clogging the porous media. The injected water will be from wastewater treatment plants with a TDS content of less 500 ppm and the TDS of recovered water in each well less than 1500 ppm. Moreover, there are criteria for selecting a domain for artificial recharge, for example, moderate transmissivity, The TDS of the aquifer should not exceed 5000 ppm, and the horizontal and vertical hydraulic gradient should be as small as possible and close to the stations suppler and demand center. The success of artificial recharge will depend on the recovery efficiency (RE) in every cycle which will increase if artificial recharge done in the correct way. The RE increases with a decrease in time between the stopping of injection and the starting of the recovery operation. Aquifer storage and recovery can play an important role as sustainability tool to resolve water resource problems, improving water quality, better than surface water storage since it minimizes construction of new infrastructure and uses that cost to initiate new desalination or waste water plants. At the end of this research we will have demonstrated the concept of the process of ASR including the volume and time for injection and recovery of water in multi-cycles and in different suitable sites.