Geophysical Characterization of Alluvial Aquifers in Plutonic and Volcanic Semi-Arid Andes Using Electromagnetic Methods

Summary Drought periods are common events in the semi-arid zone of Chile and their length and frequency has increased with climate change. Within periods of water resource stresses, subsurface water exploitation increases with the use of deeper wells for irrigation and drinking water supplies. Moreover, in case of severe droughts, aquifers could contain a reserve to mitigate the drought. Within this study, we aim to test the feasibility of electromagnetic geophysical methods to map groundwater reserve in a mountainous watershed of the semi-arid Andes, characterized by narrow valleys alluvial fillings within plutonic and volcanic sequences. The area of study is part of the Limari catchment, in the Coquimbo Region, where information about the amount of underground water available and its depth is scarce. Here we present the first results, interpretation and limitations of the application of transient electromagnetic (TEM) and magnetic resonance soundings (MRS) for the characterization of the Limari catchment alluvial aquifers.