Saltwater Intrusion and Recirculation of Seawater at a Coastal Boundary

Comparison of Seepage Simulation in a Saline Environment below an Estuary Using MODFLOW and SEAWAT

“…Motz et al [6] found that specifying equivalent freshwater heads at the brackish water boundaries in a constant-density model yielded results closest to those obtained by a variable-density coupled model. Representing the boundary conditions at the saline boundaries in constant-density models by specified freshwater hydraulic heads was also used by Simpson and Clement [29][30][31]36]. Therefore, in MODFLOW, the hydraulic heads at the lagoon bed boundary (BC) and the ocean boundary (DE) were converted to freshwater hydraulic heads using equations 2 and 4, respectively, and these boundaries were also treated as constant head boundaries.…”

“…Motz et al [6] found that MODFLOW could closely match the hydraulic heads and fluxes simulated by SEAWAT on the freshwater side of the aquifer when the coastal boundary was represented by specified freshwater hydraulic heads. Subsequently, Motz et al [36] compared coupled (densitydependent) and uncoupled (density-independent) SEAWAT solutions of saltwater intrusion and seepage circulation on the seacoast boundary of the same system described in Motz et al [6]. In that comparison study, Motz et al [36] observed that the density-independent solution produced similar results of saltwater intrusion and seepage circulation to that produced by the density-dependent solution when the ratio of freshwater recharge rate to the density-driven flux was increased.…”

“…Subsequently, Motz et al [36] compared coupled (densitydependent) and uncoupled (density-independent) SEAWAT solutions of saltwater intrusion and seepage circulation on the seacoast boundary of the same system described in Motz et al [6]. In that comparison study, Motz et al [36] observed that the density-independent solution produced similar results of saltwater intrusion and seepage circulation to that produced by the density-dependent solution when the ratio of freshwater recharge rate to the density-driven flux was increased. Thus, depending on the boundary conditions and the aquifer properties of a specific saline environment problem, it is reasonable to conclude that there may be situations when a constant-density model can replicate the results of a variable-density coupled model in simulating saline environments although that is not always the case.…”

“…Some of these comparison studies have been conducted in the context of the Henry problem [28] or on laboratory scale physical models [29][30][31][32][33] while other studies used large scale models [6,[34][35][36]. Researchers have found that under some saline conditions, a constant-density model is capable of producing results similar to a variable-density model.…”

Effect of Variable-Density and Constant-Density Representations of Flow on Simulating Terrestrial Groundwater Discharge into a Coastal Lagoon

“…In another investigation, [Arlai and Koch, 2009] compared the two solution schemes in a two-dimensional coastal aquifer of 1000 m by 100 m and they concluded that the predicted Ghyben-Herzberg interface was closely simulated by the variable-density solution and not the constant-density solution. A vertical plane model of a hypothetical coastal aquifer which is larger in domain but similar in boundary condition to Henry problem was developed by [Motz and Sedighi, 2013] and solved by the variabledensity method using SEAWAT and constantdensity using MODFLOW. Hydraulic heads and fluxes simulated by MODFLOW were found to be comparable to those simulated by SEAWAT on the model's freshwater boundary.…”