Hydrological Evaluation of the Groundwater Potential in the Fractured Karoo Aquifer Using Magnetic and Electrical Resistivity Methods: Case Study of the Balfour Formation, Alice, South Africa

Abstract

The study is aimed at evaluating the groundwater accumulations present in Alice using magnetic and electrical resistivity measurements to examine the trends of structural elements and characterize the groundwater resource for borehole drilling. The magnetic maps show a low magnetic linear structure moving northwest to southeast direction, which may be caused by fractures. The linear high intensities were probably caused by dolerite dykes, while dolerite sills caused broader high-intensity areas. The depth slices show that the near-surface magnetic structures are visible to a depth of about 19 m, and the deep-seated structures are found at a depth of about 31 m, possibly deeper. Twenty-five vertical electrical soundings (VES) of the Schlumberger array were measured with AB/2 varying between 1.5 m and 250 m across the study area. The VES interpretation showed four geoelectric layers composed of HK and HA curve types. The geoelectric layer’s thicknesses are (1) topsoil from 0.4 to 1.8 m, (2) weathered layer from 0.8 to 17.5 m, and (3) weathered/fractured layer from 9.9 to 143.9 m; the third layer could be the productive water-bearing zones, and (4) bedrock layer has an infinite thickness. The layers have resistivity values of 20-5752 Ωm, 3-51 Ωm, 136-352 Ωm, and 44-60428 Ωm, respectively. A correlation of the VES with the borehole log indicated a well-matched result. The magnetic and electrical resistivity surveys provided a detailed subsurface structure and helped identify possible fractures that could act as a passage for groundwater.

Unveiling Subsurface Characteristics of Cliff Land in Sibang, Bali Through Geoelectric Investigation

“…This supports that the type of rock is young rock with a discontinuous description (massive rock) which was destroyed by the drill bit during the drilling test [15][24] [23] [25].In the analysis of geoelectric test results and secondary data, as well as the correlation of geological data maps, it was found that the field test results matched the secondary data of geospatial data. At the geoelectric test location, BL 01-BL 06 shows that there are varying layers of soil.…”

Groundwater Potential Zones Assessment Using Geospatial Models in Semi-Arid Areas of South Africa

“…Over the years, several conventional methods, such as geological, geophysical, and hydrogeological, have been used to identify and explore GWPZ [14][15][16]. Various geophysical methods, such as electromagnetic, seismic refractive, gravity, magnetic, and electrical resistivity techniques, have been utilized in geophysics to explore groundwater [17][18][19][20][21].…”

Petrographic Analysis of the Sandstones and Mudstones in Alice, Eastern Cape Province, South Africa: Implications for Groundwater Potential

“…Many researchers have shown that diagenetic alterations in siliciclastic rocks influence the reservoir quality by changing the primary porosity and permeability of the rocks [13][14][15][16][17][18][19]. The relationship between fracture, fault, pores, and groundwater potential has been investigated and reported by some researchers [20][21][22][23].…”