Groundwater Flow Model Calibration of a Coastal Multilayer Aquifer System Based on Statistical Sensitivity Analysis

The identification of the hydrological processes taking place at coastal systems and the interaction between aquifers and the sea have been key features for many groundwater-related studies. However, the suitability of different boundary conditions for representing the hydrodynamic conditions along the coast in modelling applications is widely discussed today. In this study, a groundwater flow model is developed for a coastal multilayer semi-arid aquifer system (Lavrio, Greece), which in turn is used for the comparison between alternative boundary conditions that are considered relevant for representing the coast. The sensitivity analysis and parameter estimation of the model parameters were conducted using a statistical approach, and the results show that the head-dependent boundary condition can produce a more representative simulation of the coastal system hydrodynamics. The response of the karstic aquifer is also simulated satisfactorily, proving that the modelling code is also suitable for simulating karstic aquifers, at least at a large scale. Finally, the hydraulic interconnection between the different aquifer layers within the study area is clarified, as groundwater is primarily discharged from the karstic to the alluvial aquifer.