Hydrogeophysical Characterization of Fractured Aquifers for Groundwater Exploration in the Federal District of Brazil

Yawar Hussain,Hans-Balder Havenith,Welitom Rodrigues Borges,Rogério Elias Soares Uagoda,José Eloi Guimarães Campos,Omar Hamza

doi:10.3390/app12052509

Yawar Hussain, Hans-Balder Havenith + Show 4 more

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https://doi.org/10.3390/app12052509

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Abstract

The present study applies a geophysical approach to the Federal district of Brazil, a challenging hydrogeologic setting that requires improved investigation to enhance groundwater prospecting to meet the rising water demand. The geophysical characterization of a complex hard-rock aquifer sub-system was conducted using direct current (DC) electrical resistivity tomography (ERT) integrated with surface geological information. With a total of twenty-seven ERT profiles, the resistivity acquisition was carried out using a dipole-dipole array of electrodes with an inter-electrode spacing of 10 m. Based on resistivity ranges, the interpretation of the inverted resistivity values indicated a ground profile consisting of upper dry soil, saprolite, weathered, and fresh bedrock. Along with this layered subsurface stratigraphy, the approach allowed us to map the presence of significant hydrogeological features sharp contrasting anomalies that may suggest structural controls separating high-resistivity (≥7000 Ω m) and low-resistivity (<7000 Ω m) conducting zones in the uppermost 10 m of the ground. The assumed impacts of these features on groundwater development are discussed in light of the Brasilia aquifer settings.

Highlights

Within the Federal District (FD), the investigation was conducted in areas with the integrated supply system (Descoberto/Santa Maria—Torto system/Sobradinho Taguatinga) and in other areas located outside the integrated system (e.g., Descoberto and Santa Maria—Torto reservoirs) (Figure 1)
The main goal of the study is to investigate the hydrogeological characteristics of the aquifer sub-system-R3/Q3 of the Federal District of Brazil to improve groundwater extraction and pumping-well planning with the aid of electrical resistivity tomography (ERT) geophysical method
On the inverted resistivity tomographs, site stratigraphy and other numerous structures are delineated, which have a direct influence on the hydrodynamics of the aquifer

Summary

Introduction

Most urban aquifers are increasingly stressed due to unplanned growths of the metropolitan areas. This situation applies to the Federal District (FD) of Brazil, where the surrounding areas and agricultural activities are growing. The ongoing expansion has directly affected the availability of water as the city will reach an estimated population of 3.4 million in 2025, resulting in rising water demands [1,2]. In the past, both surface and groundwater were used to supply the city. A small portion (approximately 15%) of this supply comes from the fractured aquifer through pumping wells [3]

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