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

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 K-x when alpha(L) root KxKz >= 10 (6) m(2)/s. Here K-z is vertical hydraulic conductivity and alpha(L) is longitudinal dispersivity. Both the fresh groundwater discharge rate Q(f) and seawater recirculation rate Q(s) depend linearly on K-x. These conclusions are validated by a semi-analytical method. The increase of anisotropy ratio pushes the saltwater wedge interface seaward and reduces Q(s). The increment of the longitudinal/transverse dispersivity ratio with fixed longitudinal dispersivity decreases the slope of isosalines and Q(s). When the seabed slope angle theta increases from 0.01 to pi/2, the freshwater-seawater interface moves landward. The increment of theta increases Q(s) slightly when theta < pi/4 and reduces Q(s) when theta > pi/4. The inland recharge rate Q(f) is independent of the seabed slope. (C) 2014 Elsevier Ltd. All rights reserved.