USE OF SINGLE-POINT RESISTANCE AND SP LOGGING IN GROUNDWATER INVESTIGATION

Water is one of the abundant and widely used natural resources available to man. Many communities obtain the water they need from rivers, lakes, or reservoirs, sometime using aqueduct or canals to bring water from distant surface sources. Another source of water lies directly beneath most towns. This resource is groundwater, the water that lies beneath the ground surface. The origin of water is traced to the process of the hydrologic cycle. When rain falls on the land surface as precipitation, more than half of the water returns rather rapidly to the atmosphere by evaporation or transportation from plants. The remainder either flows over the land surface as runoff to streams, rivers, and lakes, or soaks into the ground by infiltration to form groundwater. Rivers stream and lakes make up the surface occurrence while those that sink into the ground make up subsurface occurrence called ground water.
Groundwater is the water that lies beneath the ground surface, filling the pore spaces between grains in bodies of sediment and clastic sedimentary rocks and filling cracks crevices in all types of rocks (Plummer et al 1999). The subsurface zone in which all rocks opening are filled with water is saturated zone. The upper surface of the saturated zone is the water table. Groundwater is unfortunately not evenly distributed everywhere. The distribution of ground water depends on large extent upon the types and depth of occurrences (Oseji, 2010). Ground water in its natural state tends to be relatively free of contaminants in most areas. Because it is a widely used source of drinking water, the contamination of groundwater can be a very serious problem (Plummer et al., 1999). Groundwater can be contaminated by pesticides and herbicides (such as diazion, atarzine DEA and 2, 4, D) applied to agricultural crops Can find their way into groundwater when rain or irrigation water leaches the contaminants downward into the soil; Liquid and solid wastes from septic tanlas, sewage plants and animal. Feedlots and slaughterhouse may contain bacteria viruses, and parasite that can contaminate groundwater.
Ground exploitation sometime often result in failed and abortive borehole because of lack of preliminary geophysical investigation required to map and locate prolific zones within the aquifers (Atakpo et al., 2008). In order to avoid such an occurrence and to increase the probability of drilling successful and sustainable borehole, it becomes pertinent and economically wise to carry out prior geophysical investigation. Borehole electrical resistivity and spontaneous potential method is based on the variable resistance in surface materials to the conduction of electrical current depending on materials to the conduction of electrical current depending on variation in fluid content, density and chemical composition of the composition (Paransis, 1986). Recently other electrical geophysical method such as electro-magmatic induction (EM) and ground penetrating radar (GPR) becomes increasingly popular.