Numerical simulations of steady-state salinity distribution and submarine groundwater discharges in homogeneous anisotropic coastal aquifers

Abstract

Steady-state seawater–groundwater interactions are simulated for homogeneous, anisotropic unconfined coastal aquifers using the two-dimensional numerical model MARUN. The spatial salinity distributions are approximately independent of the horizontal hydraulic conductivity Kx when αLKxKz⩾10−6m2/s. Here Kz is vertical hydraulic conductivity and αL is longitudinal dispersivity. Both the fresh groundwater discharge rate Qf and seawater recirculation rate Qs depend linearly on Kx. These conclusions are validated by a semi-analytical method. The increase of anisotropy ratio pushes the saltwater wedge interface seaward and reduces Qs. The increment of the longitudinal/transverse dispersivity ratio with fixed longitudinal dispersivity decreases the slope of isosalines and Qs. When the seabed slope angle θ increases from 0.01 to π/2, the freshwater–seawater interface moves landward. The increment of θ increases Qs slightly when θ<π/4 and reduces Qs when θ>π/4. The inland recharge rate Qf is independent of the seabed slope.