Resistivity methods used in horizontal and vertical discontinuities in the electrical properties of the ground water detection

Project Abstract

Resistivity methods are widely used in geophysical surveys for the detection of subsurface features, including groundwater. Horizontal and vertical discontinuities in the electrical properties of the ground can provide valuable information about the presence and characteristics of groundwater reservoirs. This research focuses on the application of resistivity methods to detect groundwater and investigate how horizontal and vertical discontinuities influence the interpretation of the subsurface electrical properties. Horizontal discontinuities in the ground, such as faults or changes in lithology, can create contrasts in electrical resistivity that are indicative of potential groundwater accumulation zones. By measuring and mapping these variations in resistivity, geophysicists can delineate the extent and depth of groundwater reservoirs. Vertical discontinuities, such as fractures or dykes, can also impact the electrical properties of the subsurface and affect the flow of groundwater. Understanding the distribution and orientation of these vertical features is crucial for accurate groundwater exploration. The research investigates the use of resistivity imaging techniques, such as electrical resistivity tomography (ERT) and self-potential (SP) methods, to delineate horizontal and vertical discontinuities in the electrical properties of the ground. ERT is a non-invasive geophysical method that involves measuring electrical resistivity at multiple points to create a 2D or 3D image of subsurface resistivity variations. SP surveys can complement ERT data by providing information on subsurface fluid flow and potential areas of groundwater discharge. Case studies and field experiments are conducted to demonstrate the effectiveness of resistivity methods in detecting horizontal and vertical discontinuities associated with groundwater. The research highlights the importance of integrating geophysical data with hydrogeological information to improve the interpretation of subsurface structures and groundwater resources. By combining resistivity surveys with borehole data and hydrological analysis, geoscientists can enhance their understanding of the complex relationships between geological features and groundwater occurrence. Overall, this research contributes to the advancement of groundwater exploration techniques by emphasizing the significance of resistivity methods in detecting horizontal and vertical discontinuities in the electrical properties of the ground. The findings provide valuable insights for improving the accuracy and efficiency of groundwater detection surveys, ultimately supporting sustainable water resource management and environmental protection efforts.

Project Overview

<p> </p><p><strong>Introduction</strong></p><p>The resistivity method is used in the study of the horizontal and vertical discontinuities in the electrical properties of the ground and also in the detection of three dimensional bodies of anomalous electrical conductivity. In the study of ground water movement in obubra area, the the resistivity method commonly employed are the electrical resistivity method. Electrical resistivity method is one of the most useful techniques in groundwater geophysical exploration, because the resistivity of rocks is sensitive to its ionic content (Alile, et al., 2011). The method allows a quantitative result to be obtained by using a controlled source of specific dimensions. Records show that the depths of aquifers differ from place to place because of variation in geothermal and geo-structural occurrence (Okwueze, 1996). Therefore, the need to study the area for groundwater potential especially in terms of determining the flow direction is a prerequisite for portable ground water exploration and exploitation in this area.</p><p><strong>1.1 Location And Geology Of The Area</strong></p><p>The study area lies between latitudes 50 15′ and 60 15′N and longitudes 70 45′ and 80 45′E. It is located within the sub-equatorial climatic region of Nigeria with a total annual rainfall of more than 300 to 400cm. Temperature ranged from 250C to 280C. The area experiences two seasons, these are the wet season which lasts from April to September with a peak in June and July while the dry seasons lasts from October to March (Iloeje,1991).</p><p>The study area is underlain by two major lithologic units: Crystalline basement and Cretaceous sediments. The crystalline basement rocks occupy the extreme south of the study area. Also, there are intermediate rocks scatteredin patches around Obubra, Iyamayong, Iyamitet, Ikom, Nkpani and Usumutong. The Cretaceous sediments cover about 90% of the study area. Asu River Group is the basal and oldest recorded sediment in the study area. It is dominated by bluish gray/black to olivine brown shale and sandy shale, fine – grained micaceouscalcareous sandstone and siltstone with limestone lenses. The shale is often carbonaceous and pyritic which indicates that the sediments were deposited under a poorly oxygenated shallow water environment of restricted circulation, an indication of low energy environment (Petters et al., 1987). In general, Southern Obubra lies within the Cross River plain and the clastic beds in the study area can be ascribed to the Ezillo Formation. The Ezillo Formation comprises mostly dark gray shales with fine sandstone and siltstone intercalations in the lower part, and an upper unit that is highly bioturbated, fine medium sandstone, similar to the sandstone of the Amaseri Formation. The Ezillo Formation between Appiapum and Ikom was deposited in a deltaic coastal plain, in brackish marshes and inter-distributary bays (Barth, et al., 1995). A major river (Cross River) exists in the study area into which minor streams empty their loads. The elevation of the study area ranged from 14 to 170m above sea level. The relief is characterized by undulations running at undefined direction and variably demarcating the very lowland areas from moderate relief landmarks. The occurrence of the low plains is occasionally broken by inselbergs of granite and basalts in the southern portion of the study area. In the sediment filled portions, the low plains are occasionally broken by flat -topped hills of sandstone ridges and igneous intrusive with highly ferroginized sandstones with gravels resulting from uplifts. The area is drained by the Cross River with major tributaries like, Udip, Ukong, Lakpoi, Okwo, and Okpon rivers. These rivers form a network of dendritic drainage system</p> <br><p></p>