A model for areal simulation of sea-water intrusion into coastal aquifers

A novel mathematical model for the simulation of salt-water intrusion in a phreatic aquifer has been developed The governing equations were obtained as a combination of the average over the saturated thickness for two models: a 3D density-dependent flow and transport model, and a sharp interface model The developed, MEL2DSLT, code allows simulation of the groundwater level and the averaged solute concentration in a 2D horizontal plane, together with the estimation of the salt-water depth. Governing equations were solved numerically by a finite-difference method using fully explicit schemes. The Modified Eulerian-Lagrangian Method (MEL) was implemented to overcome difficulties arising from hyperbolic behaviour of flow and transport equations, due to the advective nature of solute transport and heterogeneity of the soil characteristics (permeabilities and dispersivities). The model was verified against a numerical solution obtained for a 2D cross-sectional problem simulated by the SUTRA code To do this, the concentrations obtained by the latter model were averaged over the saturated thickness Comparisons between simulations with MEL2DSLT and SUTRA demonstrate good agreement. As a practical example, the model was implemented to simulate sea-water intrusion for the Khan Yunis portion of the Gaza Strip coastal aquifer.