Theme 2-9-Saltwater intrusion process in a layered coastal aquifer system

Abstract

Coastal regions are characterised by the interaction of land, sea and atmosphere. Therefore, sustainable management of coastal areas pre-supposes integrated management of coastal waters, coastal lands and coastal ecosystems. Among the various hydrological issues of the coastal regions, saltwater intrusion and associated problems draw special attention as it can disrupt the susceptible hydrogeological equilibrium of the coastal aquifer. Seawater intrusion in coastal aquifer may be viewed as a natural process that occurs by virtue of the density contrast between freshwater and salinewater. However, it is essential to maintain an acceptable spatial and temporal equilibrium of saltwater ingress in a coastal aquifer system. This demands quantitative understanding of the pattern of saltwater movement, mixing between fresh and salinewater, and the factors that influence such processes. Prognostic analysis of the problem by means of mathematical modelling (of flow and solute transport) can be of great use in investigating the processes. The study presented herein investigates the process of saltwater intrusion, bringing forth useful inferences on the process. Simulation of saltwater intrusion process is carried out in a multi-layered coastal aquifer system using the USGS finite element model, SUTRA. The model has been applied to the coastal aquifer system with varied boundary conditions as well as aquifer parameters, to study their sensitivities. Analysis of the extent and intensity of saltwater intrusion in the aquifer system vis-a-vis aquifer/ aquitard permeabilities, influx at the boundaries, and dispersivity of the medium has been presented.