García et al. (2025) Electrical Resistivity Tomography and 3D Modeling for Groundwater Salinity Assessment in Volcanic Islands: A Case Study in Los Cristianos (Tenerife, Spain)

Identification

• Journal: Applied Sciences
• Year: 2025
• Date: 2025-10-20
• Authors: Pedro Carrasco García, José Luis Herrero-Pacheco, Javier Carrasco, Daniel Porras
• DOI: 10.3390/app152011215

Research Groups

• Department of Cartographic and Terrain Engineering, Polytechnic School of Avila, University of Salamanca, Spain
• Técnicas Geofísicas S.L., Spain
• Geoland Services S.L., Spain

Short Summary

This study applies Electrical Resistivity Tomography (ERT) and 3D modeling in Los Cristianos, Tenerife, to characterize groundwater salinity and marine intrusion in a volcanic island setting. The methodology effectively delineates saline horizons, providing objective criteria for sustainable borehole siting for desalination purposes.

Objective

• Assess the distribution of geoelectrical domains at depth in Los Cristianos, Tenerife.
• Identify conductive horizons associated with saline waters to characterize marine intrusion.
• Establish objective criteria for optimal borehole siting for groundwater exploitation in a complex volcanic and regulatory environment.

Study Configuration

• Spatial Scale: Los Cristianos area, Arona, Tenerife, Canary Islands, Spain. Two Electrical Resistivity Tomography (ERT) profiles with effective lengths of 240 m (ERT-1) and 340 m (ERT-2). A 3D voxel model was constructed using 27 × 30 × 15 cells with a uniform 10 m resolution, reaching an investigation depth exceeding 100 m.
• Temporal Scale: The study represents a snapshot in time based on a single geophysical survey campaign.

Methodology and Data

• Models used:
  • Res2DInv software version 3.5: Used for 2D inversion of ERT data, applying smoothness-constrained least squares inversion and robust inversion schemes.
  • Oasis Montaj software Version 2025.1: Used for 3D modeling and spatial interpolation (kriging algorithms) of 2D ERT sections to generate a volumetric resistivity cube.
• Data sources:
  • Electrical Resistivity Tomography (ERT) profiles: Two profiles (ERT-1 and ERT-2) acquired using a Syscal Pro multielectrode system (Iris Instruments) with 25 and 35 electrodes, respectively, at a spacing of 10 m.
  • Electrode configurations: Both Wenner and Pole–Dipole arrays were employed.
  • Measurements: A total of 276 and 561 apparent resistivity measurements were collected for ERT-1 and ERT-2, respectively.

Main Results

• Four distinct geoelectrical domains were identified in the subsurface: a shallow domain of low to moderate resistivity (<75 Ω·m) (ignimbrites and silty sands), an intermediate–resistive domain (75–500 Ω·m) (basaltic scoria and massive basalts), a deep conductive domain (<20 Ω·m) (volcanic formations saturated with saline water), and a very high-resistivity massive basalt (>500 Ω·m) acting as an electrical basement.
• The deep conductive domain (<20 Ω·m) was consistently identified as the main marker of marine intrusion. In ERT-1, it was located at approximately 60 m depth, while in ERT-2, it appeared at shallower levels and dipped northwestward, indicating a landward progression of the freshwater-saltwater interface.
• 3D modeling successfully delineated the geometry of the saline intrusion, confirming its advance at shallower depths in the southern sector, closer to the coastline.
• Optimal drilling zones for groundwater exploitation were identified within the conductive domain (<20 Ω·m), ensuring the presence of saline water suitable for desalination and meeting regulatory requirements.

Contributions

• Demonstrates that the combination of ERT and 3D modeling is an effective, replicable, and economically efficient methodology for groundwater salinity assessment and optimal borehole siting in complex volcanic island environments, overcoming limitations of electromagnetic methods.
• Provides a novel 3D resistivity model derived from 2D ERT profiles, addressing the three-dimensional variability of volcanic formations and salinity gradients, which was often neglected in previous studies.
• Offers objective criteria for sustainable groundwater management in volcanic islands, aligning with local regulations that mandate the exploitation of saline waters for desalination to preserve freshwater reserves.
• Highlights the practical utility for the tourism sector by optimizing the location of boreholes for saline water supply, thereby reducing exploration costs and increasing project viability.
• Establishes a robust and transferable methodological framework applicable to other volcanic island environments facing similar water resource challenges globally.

Funding

This research received no external funding.

Citation

@article{García2025Electrical,
  author = {García, Pedro Carrasco and Herrero-Pacheco, José Luis and Carrasco, Javier and Porras, Daniel},
  title = {Electrical Resistivity Tomography and 3D Modeling for Groundwater Salinity Assessment in Volcanic Islands: A Case Study in Los Cristianos (Tenerife, Spain)},
  journal = {Applied Sciences},
  year = {2025},
  doi = {10.3390/app152011215},
  url = {https://doi.org/10.3390/app152011215}
}

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