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Saltwater intrusion and the recirculation of seawater at a coastal boundary have been investigated for three problems, namely the Henry constant dispersion and velocity-dependent dispersion problems and a larger field-scale problem. Based on dimensional analysis, saltwater intrusion and the recirculation of seawater can be dependent functions of as many as five independent ratios, which are (1) az, defined as the ratio of freshwater advective flux relative to the density-driven vertical buoyancy flux; (2) the aspect ratio , defined as the ratio of horizontal and vertical dimensions of the cross-section; (3) the ratio b, defined as the product of the constant dispersion coefficient treated as a scalar quantity and aquifer porosity divided by the freshwater advective flux; (4) rα = αz/αx, the ratio of the vertical and horizontal dispersivities; and (5) rK = Kz/Kx, the ratio of the vertical and horizontal hydraulic conductivities. In the two-dimensional cross-section for all three problems, freshwater inflow occurs at the upgradient boundary, and recirculated seawater outflow occurs at the downgradient coastal boundary. The upgradient boundary is a specified-flux boundary with zero freshwater concentration, and the downgradient boundary is a specified-head boundary with a specified concentration equal to seawater. Equivalent freshwater heads are specified at the downstream boundary to account for density differences between freshwater and saltwater at the downstream boundary. The effects that changing the independent ratios az, , b, rα, and rK have on saltwater intrusion and recirculation for these problems have been investigated using the numerical groundwater flow and transport code SEAWAT for two conditions, i.e., first for the uncoupled condition in which the fluid density in the flowfield is constant and then for the coupled condition in which the fluid density is a spatial function of the total dissolved solids concentration in a variable-density flowfield. |