Geoelectric applied to the 3D saline intrusion model of the Manglaralto coastal aquifer, Santa Elena-Ecuador

Abstract

Coastal aquifers are essential for the socio-economic development of coastal areas but are increasingly threatened by saltwater intrusion due to overexploitation caused by high population demand. This study aims to develop a three-dimensional (3D) model of the saline intrusion wedge using geoelectric techniques and well monitoring to improve water management in the Manglaralto coastal aquifer. The methodology includes: i) a technical description of the current situation, ii) the application of geoelectric methods such as electrical resistivity tomography (ERT) and well monitoring, iii) the development of a 3D model using Geomodeller, and iv) the proposal of management strategies for coastal aquifers. The results reveal the presence of salt wedges during both rainy and dry seasons. The main factor conditioning advance of saline intrusion is overexploitation of wells, with February showing the highest water consumption. Evapotranspiration and increased water consumption (reaching 74,546 m³ during the rainy season) limit natural and artificial recharge. However, in the dry season, a 20% reduction in water consumption refreshes the aquifer, and recharge has a more significant influence. The implementation of a "tape" (dyke) mitigates the advancement of saline intrusion, enhancing aquifer recharge at a rate of 4,200 m³/m·day in August. The resulting 3D model highlights a dynamic system that requires continuous monitoring and management to support sustainable water resource planning.