Predictive Simulation of Seawater Intrusion Control Measures in a Coastal Aquifer

Many coastal aquifers are facing seawater intrusion due to overexploitation of freshwater. In this study, the groundwater flow and solute transport in a coastal aquifer of Minjur, in India was simulated considering the possible cases of aquifer recharge, freshwater draft, relocation of pumping wells etc. using numerical modelling software. The groundwater flow model MODFLOW and solute transport model MT3D were calibrated for a seven- year period and validated against dataset for two years, which gave satisfactory results. The sensitivity analysis of model parameters revealed that hydraulic head was greatly influenced by the horizontal hydraulic conductivity.The model was used to predict the response of coastal aquifer to four potential scenarios like aquifer recharge, reduced pumping, relocation of pumping wells and a combination of these scenarios. Effectiveness of various management scenarios was evaluated based on their ability to improve groundwater level and salinity in observation wells/piezometers, to reduce the affected area and restrict the advancement of seawater-freshwater interface. The result of predictive simulation indicated that the combination of scenarios such as reduction in ground water pumping by 25% from semi confined aquifer, increased pumping by 25% from unconfined aquifer, increased recharge fromrivers byconstructing check dams have the potential to restrict the seawater-freshwater interface movement and improve groundwater quality in Minjur aquifer. These control measures would be effective in shifting the interface towards the coast by 1.0 km in unconfined aquifer and 1.5 km in semi confined aquifer by the year 2025.