Submarine groundwater discharge: Effects of hydrogeology and of near shore surface water bodies

Abstract

Submarine groundwater discharge is investigated numerically for a confined aquifer considering three types of permeability distribution (uniform, anisotropic and heterogeneous lognormal) as well as for an aquifer in which a surface water body is embedded. The latter case corresponds to aquifers with lagoons, flat lakes or wetlands near the coast. The numerical simulations are performed using the code FAST-C(2D), developed by Holzbecher (1998). For the confined aquifer, the portion of recirculated seawater in submarine groundwater discharge and the length of the recirculation zone are investigated. The parameters influencing these variables in the case of homogeneous aquifer (isotropic or anisotropic) are discussed. Further, the validity of a linear relationship between the submarine groundwater discharge and the flux of terrestrial groundwater toward the sea, proposed by Destouni and Prieto (2003), is investigated. As far as possible, our results are compared with results presented by Smith (2004), which were obtained using different codes. The investigation of a heterogeneous model aquifer concerns the influence of the variability of the permeability distribution on the portion of recirculated seawater and is performed by means of Monte Carlo analyses. Finally, for coastal aquifers in which surface water bodies are embedded, the main flow features are investigated. Particularly, the pathway of terrestrial groundwater to the sea, the flux of groundwater of marine origin to the surface water body, the recirculation of seawater and the flux from the surface water body to the sea have been considered. The parameters influencing these fluxes, which are important for the transfer of pollutants and tracers from the groundwater to the surface water and to the near shore seawater, are discussed.