A Multi-Tool 3D Conceptual Model to Elucidate Groundwater Processes, Vulnerability, and Recharge Patterns in a Semi-Arid Region: A Case Study from Morocco

Under arid and semi-arid climatic conditions, groundwater is a basic resource to meet the requirements of socioeconomic development. Better conservation of this resource requires understanding the functioning of aquifer systems by informing about the degree of its vulnerability, the hydrochemical processes that control it, as well as the mode and origin of groundwater recharge. The location of vulnerable recharge areas is of crucial importance for the protection and rational management of groundwater, particularly in arid and semi-arid areas where a systematic monitoring and the master of pollution sources are lacking. In this context, this study aims to develop a 3D conceptual model of the Chiadma-South aquifer system (Essaouira basin, Morocco) based on hydrochemical, isotopic data and the DRASTIC model. The vulnerability and NO 3 − contents maps show that the upstream part and the downstream part of the study area are the most threatened by intrinsic pollution. The chemical characterization of the investigated aquifer shows that the mineralisation is governed by the dissolution of the surrounding formations, and evaporation phenomena and no seawater intrusion has been detected. The isotopic characterization of the input signal displayed that precipitation replenishing groundwater within the catchment have an Atlantic fingerprint, with the evaporation focused on the midstream part in the North and the upstream part in the South. However, visualisation of all highlighted processes under a 3D conceptual model could be a support for decision-makers to implement a rational management strategy for the vital resource of the study area.