Assessment of Groundwater Yield Potentials Zones of Idi-Ayunre using Vertical Electrical Sounding and Geographic Information System (GIS)

Abstract

To fully harness the increasing number of observations and variant data sets available and put them to efficient use in geological studies aimed at solving earth science-related problems, GIS technique is a veritable tool. The dynamic techniques and the complex nature of earth sciences is a serious cause for worry for geologists. In this work vertical electrical sounding (VES) was integrated with geographic information system (GIS) to delineate subsurface characteristics and evaluate groundwater potential zones in Idi Ayunre, Oluyole Local Government Area, Oyo State. The results of the VES curves obtained from the partial curve matching were used to constrain the interpretation by the computer using iteration software known as WINRESIST® and extended analysis on the data set was done using geostatistical analysis tool on archGIS 10.0®. The Root Mean Square (RMS) errors for the analysis were found to be very low with an average of 2.96% . This underscores the reliability of the analysis tool for this type of work. The area is dominated predominantly by Type-H curves which amassed twenty (20) out of the twenty-one (21) VES and one (1) VES producing a type-K curve. The VES results revealed a maximum of three geo-electric layers, viz: topsoil, weathered layer, bedrock respectively. The yields of wells dug in most of these locations may be insufficient, even for domestic use because of its relatively small thicknesses. However, at a depth of 7.8 m, a fractured zone occurs in VES 10 with resistivity value of 21.2 Ωm suggesting the presence of groundwater, which may be considered the main aquifer units suitable for groundwater exploration.

Keywords

• geographic information system
• aquifer
• vertical electrical sounding
• electrical resistivity
• basement complex