Geoelectric Exploration for Groundwater using Resistivity Data

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Published on International Journal of Biology, Physics & Matematics
ISSN: 2721-3757, Volume 1, Issue 2, page 14 – 23
Publication Date: 22 November 2018

Ikechukwu E. Nwosu & Happiness N. Iwuoha
Department of Physics, Imo State University
Owerri Nigeria

Journal Full Text PDF: Geoelectric Exploration for Groundwater in Mbaitoli L.G.A. Imo State Nigeria using Resistivity Data.

Geoelectric survey carried out at Mbaitoli in Imo State of Southeastern Nigeria has shown that there is a potential for groundwater resource in this region. Vertical electric sounding utilizing the Schlumberger electrode configuration was used to survey 10 fairly well distributed points within the study Area. Interpretation of resistivity data within the area revealed 5-6 geoelectric layers within the area. The VES data was acquired using a resistivity metre with a maximum half current electrode separation of 400m. Furthermore the acquired data were interpreted using the combination of curve matching and computer iterative modeling techniques involving the Schlumberger software version 9.2. Results of the study revealed that aquifer depth varied from 83.2m at Alaenyi Ogwa to 169m at Umuduru Ifeakala with a mean value of 138.22m.The apparent resistivity varied from 338ohm-m at Obokpo Ubomiri to 161,000ohm-m at Ihite Afara with a mean value of 5,2904.8ohm-m. Aquifer thickness ranged from 24.9m at Umuowa Obokpo to 73.9m at Odumara Obi Orodo with a mean value of 48.81m.

Keywords: Apparent Resistivity, Aquiferous Zones, Geoelectric Layers, Geometric Factor, Schlumberger Configuration.

1. Introduction
This paper describes a geoelectric exploration for groundwater undertaken at Mbaitoli L.G.A. of Imo State, Southeastern Nigeria. The objectives are to study the occurrence of ground water in the Mbaitoli area of Imo State, determine the depth to water table and obtain the thickness of aquiferous zones.
Groundwater is the water found underground on the cracks and spaces of soil, sand, and rocks where it is stored and moves slowly through geologic formations (called aquifers). Groundwater is globally important and a valuable renewable resource for human life and economic development. An estimated 2 billion people worldwide rely on ground water for their drinking water supply Morris et al (2003).
In general, geoelectric measurements enable the electric resistivity of the subsurface to be determined. The interpretation of data from such measurements yields useful information on the structure and composition of these subsurface layers. Resistivity techniques are well established and widely used to solve a variety of geotechnical and geological problems (Ward; 1990). The primary purpose of the resistivity method is to measure the potential differences on the surface due to the current flow within the ground. Many research works have been done using electrical resistivity method. These include; Uma (1989) who carried out a study on the groundwater resources of Imo river basin using hydrological data from existing boreholes and concluded that three aquifer systems (confined, unconfined and semi-confined aquifers) exist in the area. Mbonu, et al (1990) carried out seventeen Schlumberger vertical electrical soundings (VES) in parts of Umuahia area for the generation of aquifer parameters. Agbodike I.I.C. et al (2013) used electrical resistivity method to determine the depth and thickness of the aquiferous zones in the Oru area of Imo-State ……..

2. Location and Geomorphology of the Study Area
The survey area lies within latitudes 50 31’N and 50 4’N and longitude 60 56’E to 70 08’E (Ofodile, 2001). The designated area covers about 204km2. It has a population of 237,555 with 31 autonomous communities. The town comprises such communities as Umunoha, Afara, Ifakala, Orodo, Ubomiri, Egbeada, Idem Ogwa, Awo Mbieri, Alaenyi Ogwa, Abazu Ogwa and Ochi Ogwa among others Emmanuel et al (2014). The map of this study area is shown in figure 1. It lies within the tropical rain forest belt of Nigeria with luxuriant growth of trees, it has humid tropical climate with high temperature and seasonal rainfall. Two main climate seasons characterized the study area namely: dry and rainy seasons. The rainy season starts from April to October with a mean annual rainfall of about 1,500mm to 2000mm. The dry season extends from November to March, in between this period harmattan occurs. The area has an average annual temperature above 200C which creates an annual relative humidity of 75%. The study area is drained by both surface water and groundwater ………