DELINEATION OF AQUIFER DEPTHS AND ITS CHARACTERISATION USING GEOPHYSICAL METHOD

CHAPTER ONE

1.0       INTRODUCTION

1.1    BACKGROUND OF STUDY

Water is a necessary liquid for human life and the survival of the ecosystem. Water must have certain physical properties that ensure its wholesomeness: it must be colorless, odorless, tasteless, and easily foam with soap or detergents. Because the human body and blood are composed of 60-75% water, adequate water is required; at least 2-3 litres for adults to improve the effective functioning of the circulatory and metabolic systems of the body. Domestic (drinking, washing, bathing, and cooking), agricultural, industrial, and recreational activities all require safe water. This water comes from a variety of sources, including rain, snow, streams, lakes, rivers, the sea, and aquifers (groundwater). The chemical components of water determine its safety.

Groundwater is a valuable natural resource.

provides billions of gallons of water for domestic, agricultural, industrial, and other purposes. Because the known surface water bodies in the study area have been severely polluted by anthropogenic activities, approximately 85% of the area’s population now relies solely on groundwater as their source of water. As a result, harnessing and preserving clean and safe groundwater becomes critical.

The significant thickness of the aquifers, the high transmissivity of water through these aquifers due to the high degree of porosity and permeability, and the adequate groundwater recharge capacity enhanced by the area’s high annual rainfall make the aquifers of the area reliable water resources capable of yielding and supplying reasonable millions of volume of water to meet the water needs of the area.

the area’s people and industries through both public and private abstractions (Todd, 1959; Krivochieva and Chouteau, 2003, Tamunobereton-ari et al, 2010a; Tamunobereton-ari et al, 2010).

Water samples from some existing wells and boreholes in the study area fall short of acceptable groundwater characteristics, and during the dry season, most wells and boreholes drop to a minimum yield and sometimes dry up; possibly due to a lack of hydrogeological information about the area and improper aquifer delineation to facilitate precise identification of desired aquifer.

The geoelectrical or electrical resistivity method is well established as a quick, non-invasive, and cost effective method of subsurface characterization. These combined hydro-geophysical methods, which use vertical electrical sounding in conjunction with 2D wenner electrical resistivity tomography (ERT), are primarily used for hydro-geological investigation aimed at aquifer characterization and ground water quality studies (Olayinka and Mbachi, 1992; Ismail Mohamaden, 2005; Astahani, 2006; Bello and Mankinde, 2007 in Mogagi et al, 2011).

These methods image the subsurface geologic stratigraphy for subsurface characterization in order to delineate zones with high porosity, permeability, and saturation for adequate ground water exploitation and determination of depth, thickness, and boundary between saline and potable fresh water aquifers.

zones (Khalil, 2006; El-waheidi et al, 1992; Bello and Mankinde, 2007; Astahani, 2006; Ismail Mohamaden, 2005). (Khalil, 2006; El-waheidi et al, 1992; Bello and Mankinde, 2007; Astahani, 2006; Ismail Mohamaden, 2005). Ground water exploration entails employing a variety of geophysical techniques in the search for water-bearing rocks known as aquifers (Ariyo and Adeyemi, 2012; Emenike, 2001). Aquifer is defined by Mogaji et al. (2011) as any mass of permeable rock material from which a significant amount of water can be recovered. Because Sabongida-Ora Edo State has few boreholes and ephemeral streams, water is a valuable commodity.

Water in sufficient supply and quantity is a requirement for all life, both domestic and industrial (Ariyo and Adeyemi, 2012). This research sought to shield light on subsurface geology in order to determine geo-electrical potential.

and hydro-geophysical characteristics of potable aquifer for optimal groundwater exploration. In this study, both Schlumberger and Wenner array configurations were used.

Because the Schlumberger method penetrates deeper than the Wenner method, it is better suited for depth and thickness investigations, whereas the Wenner configuration discriminates between resistivities of different geoelecric lateral layers (Olowofela et al, 2005 cited in Adegbola et al, 2010). As a result, the use of hydro-geophysical methods reveals the existence of a perched water aquifer within a depth window of 15m to 35m and a deep seated confined aquiferous unit beyond 240m with good characteristics for potable water exploration and supply in the study area.

Methods for using geophysical techniques in groundwater exploration have already been presented (Van Dongen and colleagues). Woodhouse 1994), but, as MacDonald et al. (2001) pointed out, “areas with complex geology and hydrogeology are not covered by the general approach and require special methods for specific problems”. Many geophysical methods have been used for groundwater resource investigation, but the electrical and electromagnetic methods have had the most success and can be used for studying fresh and/or contaminated aquifers all over the world (Meju et al. 1999; Peavy and Valentino 1999; Srensen and Sndergaard 1999; Gwaze et al. 2000; Corriols et al. 2000; Mendoza et al. 2000; Miele et al

1.2    STATEMENT OF THE PROBLEM

The groundwater potentials and surroundings are enormous, based on positive indicators such as high resistivity values, clean coarse sand formation materials, the thickness of the established aquiferous saturated zone, and the shallow depth to locating the aquifer, which is approximately 22m, which can facilitate the easy harnessing and supply of safe, sustainable, and portable water to the people of the area. A lack of expertise could be a major issue that leads to poor water production or drilling. This is a situation in which drillers are unable to properly decipher the fundamentals of borehole drilling and simply stop working without knowing what to do. Finally, several studies on aquifer delineation have been conducted. depth, but not a single study has been conducted on the delineation and characterisation of aquifer depths using geophysical methods.

1.3    AIMS AND OBJECTIVES OF STUDY

The primary goal of the research is to investigate the delineation of aquifer depths and their characterization using geophysical methods. Other specific study objectives include:

1. to ascertain the depth to bedrock aquifer thickness.

2. to identify appropriate areas for borehole development.

3. to ascertain the approximate depths of the proposed boreholes.

4. to ascertain the factors influencing aquifer depth.

5. to proffer solution to the problems.

1.4    RESEARCH QUESTIONS     

1. What is the depth to the bedrock aquifer thickness?

2. What are the best locations for borehole development?

3. What is the estimated depth of the proposed boreholes?

4. What are the factors influencing aquifer depth?

5. What are the potential solutions to the problems?

1.5    SIGNIFICANCE OF STUDY

The study on the delineation of aquifer depth and its characterization using geophysical methods will benefit the entire country because it will educate the government on the various techniques for delineating aquifer depth. It will also advise them on the topological area that is suitable for the establishment of public boreholes. Finally, the study will add to the body of existing literature and knowledge in this field of study, as well as serve as a foundation for future research.

1.6    SCOPE OF STUDY

The study of aquifer depth delineation and characterization is limited to geophysical methods.

1.7    LIMITATION OF STUDY

Financial constraint- Inadequate funding tends to impede the researcher’s efficiency in locating relevant materials, literature, or information, as well as in the data collection process (internet, questionnaire and interview).

Time constraint- The researcher will conduct this study alongside other academic work. As a result, the amount of time spent on research will be reduced.

1.8    DEFINITION OF TERMS

Delineation To describe or mark something’s edge:

Aquifer

An aquifer is a subterranean layer of permeable water-bearing rock, rock fractures, or unconsolidated materials.

Depths are the distances between the top or surface of something and its bottom.

Characterisation A description of someone’s or something’s distinguishing characteristics.

Geophysical science is concerned with the physical processes and physical properties of the Earth and its surrounding space environment, as well as the use of quantitative methods to analyze them.

Method A method of accomplishing or approaching something, especially one that is systematic or established.

 

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