31. Motion of Seawater Interface Due to Freshwater Injection Seawater Extraction Barriers

Transient motion of seawater-freshwater interface in coastal confined aquifers due to a series of injectionextraction well system is studied using an areal finite element model. The seawater near the coast is extracted by a series of wells located parallel to the coast and the freshwater is injected by a series of wells inland. The combined action of freshwater ridge formed by the injection wells and the extraction trough formed by the extraction wells resulted in a reduction of intrusion up to 80%. The well spacing affects the performance of the wells significantly and the spacing of less than10% of the initial intrusion length was found to be effective in controlling the intrusion. Performance of the combined system of wells proved to be significantly better than the series of seawater extraction wells alone. The results from the present study would be useful in designing the system of injection-extraction wells in coastal aquifers to combat seawater intrusion.