Steady-state behavior of coastal and insular groundwaters: sand tank experiment

The steady-state behavior of coastal and insular groundwaters was investigated using a sand tank. In the case of seawater intrusion into confined coastal aquifers, the fresh-water/salt-water inter-faces simulated by the boundary element method (BEM) exhibited a good agreement with those by experiment. Dupuit's assumptions are appropriate to apply in case of lower hydraulic gradients. In the hydrodynamic dispersion model, the isoplethic patterns of salt concentration in a case of velocity-dependent dispersion coefficient agree better with those by experiment than in a case of the constant dispersion coefficient, and Cauchy's boundary condition is rather realistic. In a case of freshwater lenses, the fresh-water/salt-water interfaces reproduced by the analytical solution exist slightly above the experimental visual interfaces, and the hydrodynamic dispersion model simulated the transition regions comparatively well.