Groundwater Flow Simulation in Coastal Aquifers Using the MODFLOW Algorithm

Abstract

The over-extraction and saltwater intrusion of coastal aquifers is a growing problem that threatens the 
availability of freshwater for agriculture, industry, and domestic purposes. For effective, sustainable management of 
groundwater resources, it is necessary to understand and predict the complex dynamics of groundwater flow in these 
systems. This study is focused on simulating three-dimensional flow behavior in a representative coastal aquifer using 
the MODFLOW algorithm, a modular finite-difference groundwater flow model developed by the USGS. The model 
simulates key hydrogeological parameters, including hydraulic conductivity, specific yield, aquifer stratification, and 
boundary conditions, and is calibrated using observed groundwater head data from monitoring wells."Special attention 
is given to the freshwater–saltwater interface modeling with the SEAWAT package that accounts for variable-density 
flow, which is compatible with MODFLOW. Results showed that pumping near the coast changes the flow direction 
while accelerating saltwater intrusion. However, enhancement of recharge and optimization of well-field positioning 
inland can alleviate these risks. The simulation results confirmed the effectiveness of MODFLOW as a decision
support tool in the management of coastal groundwater resources by predicting various scenarios of aquifer 
sustainability with differing recharge and pumping rates.