MODELING OF SEA WATER INTRUSION AND POSSIBLE SCENARIOS FOR GROUNDWATER USE: THE CASE OF THE TUNIS COTE ORIENTALE AQUIFER

Abstract

The Cote-Orientale coastal aquifer in northeastern Tunisia, covering 430 km², is under increasing pressure from intensive groundwater abstraction for irrigation. This study investigates the spatial and temporal evolution of seawater intrusion and evaluates management strategies using a coupled groundwater-flow and solute-transport model. A MODFLOW model was developed and calibrated under steady-state conditions using hydraulic-head, recharge, and abstraction data for 2004. A nine-layer SEAWAT model then simulated variable-density groundwater flow and salinity transport. Calibration produced root mean square error values of 2.98 m for hydraulic head and 2.54 g/L for total dissolved solids. The calibrated model indicated that seawater intrusion extends approximately 2–3 km inland and intensifies with depth, while upconing further increases salinity locally. Scenario simulations showed that increased abstraction accelerates the inland migration of the saline front, whereas reduced abstraction promotes its gradual long-term retreat. Relocating coastal wells farther inland without reducing total abstraction was ineffective. These findings demonstrate that controlling total groundwater abstraction is more effective than well relocation alone and provide a basis for sustainable management of vulnerable semi-arid coastal aquifers.