Finite element modelling of seawater intrusion in Wadi Ham aquifer, UAE

Purpose - Seawater intrusion represents a major problem in many coastal aquifers all over the world. It degrades the water-quality and hence the groundwater may become unsuitable for domestic and agriculture purposes. Due to the direct hydraulic contact between the freshwater and saline water in coastal aquifers and the density difference between the two water bodies, the seawater migrates inland. The problem is exacerbated when the groundwater abstraction rates exceed the natural recharge from rainfall events. The key to controlling this problem is to maintain the proper balance between water being pumped from the aquifer and the amount of water recharging it. The purpose of this paper is to present a coupled transient finite element model for simulation of fluid flow and solute transport in soils with application to study seawater intrusion in coastal aquifers. Design/methodology/approach - The model includes coupling of fluid flow and solute transport. Transient density-dependent flow and the dependency of dispersion on velocity are considered. After validation, the model is applied to predict the seawater intrusion in the Wadi Ham aquifer, UAE in vertical sections and the results are compared with those from a commercial code (SEWAT) which was used to simulate seawater intrusion in the aquifer in a horizontal section. Findings - A good agreement is observed between the results of the current model in the vertical cross-section and those of SEWAT in the horizontal cross-section for the case of Wadi Ham. The results show that the model can predict the extent of seawater intrusion (and the transition zone) and distribution of salt concentration in the aquifer with a good accuracy. Originality/value - The developed model includes coupling of fluid flow and solute transport in saturated and unsaturated porous media. Transient density-dependent flow and the dependency of dispersion on velocity are considered. The model has been applied to a real world case study. A combination of the results in vertical and horizontal sections has been used to build a 3D picture of seawater intrusion in the aquifer.