The influence of submarine groundwater discharge on coastal zones : the case of two Mediterranean lagoons.
In the past ten years, many studies focused on the importance of submarine groundwater discharge (SGD) on coastal processes. SGD consists of terrestrial fresh groundwater and seawater recirculating across the aquifer - ocean interface. It provides an important transport pathway for nutrients and chemical pollutants entering the marine environment. It has been recognized that it can strongly influence coastal-water and geochemical budgets and drive ecosystems change. A lot of studies allowed to develop new methods and tracers techniques for identifying and quantifying such processes.
Two Mediterranean sites have been studied in this context. In both site, we used a water balance method approach completed by a multi-element study, with a special interest in radium (226Ra and 228Ra) and radon (222Rn) isotopes analysis.
In the Camargue delta, (GIZCAM project), the groundwater discharge in the Vaccares lagoon was estimated from 222Rn mass budgets. It is around 1 105 m3/d, in very good agreement with those based on hydrological and salt budget. In the South basin of the Venice Lagoon, Italy, (CORILA project), the subsidence of the basin prevents the fresh groundwater discharge induced by the hydraulic gradient. Our work is thus focused on the characterization of the recirculated saline groundwater discharge (location, speed, induced changes in water chemistry). This discharge appears mostly driven by tides as this is the Mediterranean place where the tidal variation is the most important.
HyMeX – Hydrological cycle in the Mediterranean Experiment 2010-2020