Three-Dimensional Numerical Simulation of Saltwater Extraction Schemes to Mitigate Seawater Intrusion due to Groundwater Pumping in a Coastal Aquifer System

Abstract

A series of three-dimensional numerical simulations using a multidimensional hydrodynamic dispersion numerical model was performed to analyze various saltwater extraction schemes for mitigating seawater intrusion attributed to groundwater pumping in a coastal aquifer system. A steady-state numerical simulation was performed first to obtain initial (i.e., pregroundwater pumping) steady-state conditions before groundwater pumping, and then a transient-state numerical simulation was performed to obtain intermediate (i.e., postgroundwater pumping) steady-state conditions during groundwater pumping. In the subsequent series of transient-state numerical simulations as scenario and sensitivity analyses, four different saltwater extraction factors such as the amount of saltwater extraction, the number of extraction wells, the horizontal location of extraction wells, and the vertical interval of saltwater extraction were considered to determine an optimal saltwater extraction scheme for the coastal aquifer system threatened with seawater intrusion. The numerical simulation results show that seawater intrusion may be better mitigated when saltwater is extracted at 30% (up to 50%) of the groundwater pumping rate from a single extraction well, which is located horizontally midway between the pumping well and the coastline and is screened through the whole sand aquifer.