Understanding Saltwater Intrusion Processes Using Laboratory-Scale Physical Models

The objective of this research is to develop a better fundamental scientific understanding for saltwater intrusion and the associated transport processes occurring in coastal groundwater aquifers.   Results of two sets of laboratory experiments will be presented.  The first set of experiments simulated the transient movement of salt wedge in a coastal aquifer.   The experiments were completed in a laboratory-scale sand tank model fitted with boundary conditions that can deliver two types of groundwater fluxes—areal-recharge flux and regional flux.  The experimental results were modeled using the numerical code SEAWAT.  Based on the transient salt wedge migration data collected from the study, we hypothesized that when the fluxes are perturbed, it would require relatively less time for a salt wedge to recede from an aquifer when compared to the time required for the wedge to advance into the aquifer.  This, rather counter intuitive, hypothesis implies that saltwater intrusion and receding processes are asymmetric and the time scales associated with these processes are different.  We use a combination of laboratory and numerical experiments to test this hypothesis and use the resulting dataset to explain the reason for the difference in salt wedge intrusion and recession time scales.  The experiments were simulated using a numerical model.   The laboratory data and the model results were then used to develop better understanding of the transport processes occurring beneath a steady-state salt wedge.