GEOPHYSICAL INVESTIGATION OF GROUNDWATER LEVEL USING VERTICAL ELECTRICAL SOUNDING

ABSTRACT

A geoelectric survey of groundwater potential was carried out in the male hostel at Isa Kaita College of Education Dutsinma, Katsina State Nigeria using ABEM SAS 300 Terrameter. The Wenner and Schlumberger electrodes configurations were used for data acquisition. In the process, four Vertical Electrical Soundings (VES) were conducted at stations 01, 02, 03, and 04 covering the area. This was done in order to determine: the variation in resistivity of the topsoil of the area, the Depth and the thickness of the weathered basement, the depth and the thickness of the Aquifer, the Depth to basement, and to establish areas suitable for borehole development. The VES data obtained were interpreted using ipi2win computer software which showed that the area is composed mainly of three (3) layers, namely; the topsoil, weathered basement, fractured basement. The weathered and fractured layers constitute the aquiferous zone in all the stations. The results of the interpreted VES data showed that the first layer has resistivity of the topsoil varies from 18.2 to 172 Ωm with an average value of 95.1 Ωm. The thickness of the weathered basement varied from 10.8 to 16.2 m with an average value of 13.5m while depth to this layer varies from 10.8to27 m with an average value of 24.3 m. The thickness of the fractured basement varied from 16.2 to 2.14 m with an average value of 18.34 m, while depth to this layer varies from 27m to 4.33m with an average value of 15.67 m. The thickness of the aquifer varied from 16.2mto 2.14 m with an average value of 18.34 m, while depth to aquifer varies from 27 to 4.33m with an average value of 15.66 m. Depth to basement varies from 27 to 4.33m with an average value of 15.67 m. Based on the results, VES 01 has high potential for groundwater and are therefore recommended for borehole establishment

CHAPTER ONE

INTRODUCTION

1.1 Background of study

Water is useful natural resources that are not only essential for the survival of mankind but also for the survival of the natural environment. The availability of water has played a key role in development of all civilizations. Indeed especially in the ancient times, water scarcity prevents the development of settlement. Social welfare and economic development may be hampered in the absence of reliable water supplies. Water is essential to people and the largest available source of fresh water lies underground. Increased demands for water have stimulated development of underground water resources (Afuwai, 2013). This is particularly true of sub-sahara and sahara countries, such as Nigeria where water resources are extremely limited and highly valued as a social and economics good. However water is available in many forms such as ice caps, glaciers, ocean water, surface water and groundwater.

Groundwater happens to be a more reliable source of water for over half of the world population (Alabi,A.A.,R. Bello, A.S.Ogungbe and H.O. Oyerinde, 2010). It is described by Otutu and Oviri (2010) as water found in the saturated layers of soil and rocks. In other to explore this natural resources for the benefit of sustaining life, various geophysical survey has been employed successfully. These method include electrical resistivity surveys, seismic refraction, electromagnetic, gravity, magnetic and magneto telluric (Karami, B.,K.N.Dhumal,M. Golabi and N. Jaafarzadeh, 2009; Majumdar and Das, 2011;Todd 2004). The choice of method used depends largely on the depth of investigation and sometimes cost (Todd, 2004; Majumdar and Das, 2011). Of all these method used in exploring for groundwater, electrical resistivity profiling has been the most widely used method (Molua and Eagbetere, 2005). This is because the operation of the field instrument is uncomplicated and the analysis of data is less unwidely and economical. Geo-electrical resistivity has been developed greatly and has become an important instrument in hydrological studies, mineral prospecting and mining as well as in environment and engineering application. (Alile , 2011; Griffiths and baker, 1993; Dahlin and loke., 1996). This underlying principle of measuring substance variation using electrical resistivity within the earth was developed by Schlumberger who conducted the first experiment in the field of Normandy and the same idea was also developed by frank Werner in the United States of America. This geo-electrical resistivity method has been found useful in locating groundwater in fissured rock, mapping of plumes, mapping of boundaries of saline groundwater and exploration of geothermal fluids. However; geo-electrical resistivity surveys have undergo significant changes in the last three decades.

The traditional horizontal layering technique for investigating geo-electrical resistivity data are rapidly being replaced with 2-dimentional and 3-dimentional models of interpretation especially in complex and heterogeneous subsurface media. Field techniques have advanced from manual measurements made at separate and independent points to the use of automated machine called terrameter with multi-electrode array along the measurement profile. Till 1980s, data acquisition was more or less carried out manually and this is demanding slowly and the quality of the measured data is poor. Therefore range of fast automated multi-electrode and multichannel data acquisition system now exists that follows flexibility in the acquisition of geo-electrical resistivity data. (Barker, 1981; Stummer and Maurer, 2001; Auken et al., 2006).As a result of these successful applications of electrical resistivity method over the years in groundwater exploration, this prompted the researcher to adopt Electrical resistivity method to carried out investigation on groundwater potential at male student resident at the Isa Kaita College of Education and geological structure of the sturdy area.