Sustainable groundwater management in an arid hardrock-alluvium Al-Fara aquifer, Oman

Wadi Al-Fara catchment, located at the northwest of Oman, represents one of the most promising areas for the sustainable agricultural and urban developments. Groundwater resources have been substantially overexploited to provide irrigation, industrial and domestic demands leading to a dramatic decline of the water table in the coastal zone of the catchment. This situation has compelled the initiation of comprehensive mitigation strategies and tools for the sustainable groundwater resources. Understanding of the aquifer conditions and groundwater resources availability are crucial steps towards their proper management. Groundwater numerical modeling is an important tool to achieve the stated steps. A three-dimensional stratigraphic model of the study area representing the vertical and spatial extent of four principal hydrogeological units was generated using data collected from 57 drilled borehole logs. Layer elevations and materials for six layers grid cells were taken from the generated stratigraphic model in which the materials and elevations were inherited from the stratigraphic model that encompasses the cell. This process led to an accurate grid so that the developed conceptual model was mapped to simulate the groundwater dynamics from October 1993 to September 2013. A triad (stress period, time step, and time unit) was specified as (monthly, monthly, and daily), respectively. A regular mesh and a block centered finite difference grid with 0.125 km2 cells (500×500 m) with a total of 150 rows, 97 columns and 6 layers were considered. Simulations showed a long-term water balance deficit as the abstraction (51 Mm³/yr) exceeds natural recharge (31 Mm³/yr). Recharge flux from the highland to the coastal zone is a major contributor (12 Mm³/yr) to water resources in the coastal plain, sustaining the hydrological system along the southern margin by flow from the storage in the adjoining highland-fractured aquifers. The calibrated and validated model was used to conduct long-term simulations (horizon 2013-2033) to examine the impact of four management scenarios on the groundwater balance and groundwater level: - Scenario 1: Evaluate the current aquifer depletion with no interventions to 2033 - Scenario 2: Evaluate the aquifer condition with no recharge - Scenario 3: Evaluate reduction of the current abstraction to achieve the equilibrium condition - Scenario 4: Evaluate aquifer's response to increase by 30% the pumping rate in the future to cover the growing water demands The results revealed that further development of the aquifer will result in a serious imbalance between inflows and outflows leading to a progressive rate of sea water intrusion and decline in the water table.