Assessment of groundwater geology, viability and vulnerability of Ikeduru/Mbaitoli Area, Imo State, Nigeria, using resistivity data

Abstract

This study was conducted by obtaining twenty three vertical electrical sounding (VES) survey data with the use of the Schlumberger configuration mode. The data were gotten with a maximum current electrode spread of 400m using the ABEM Terrameter SAS 4000. Then, four parametric soundings were carried out at the location of existing boreholes where pumping test data were available, for calibration, correlation and control. The data were analytically processed using Longitudinal conductance and DRASTIC index methods. Information extracted were then used to evaluate the vulnerability as well as the viability of the aquifer potentials of the study area. Longitudinal conductance increases in SW and NW trends. The highest value occurs at Ochii Ogwa (0.09) and lowest at Akabo Ikeduru (0.004).The DRASTIC method uses seven parameters, viz: Depth to groundwater table, net Recharge, Aquifer media, Soil media, Topography, Influence of vadose zone and hydraulic Conductivity, and were used to produce vulnerability map. Result of the vulnerability assessment from the vulnerability mapshows that the area has55%low vulnerability from 103 to 107, 30% moderate vulnerability from 108 to 114 and 15% high vulnerability from 115 to 118 of the DRASTIC index to groundwater contamination. The assessment was needed because prevention of contamination, monitoring and management of the aquifer was necessary to increase the efficient use of the current water supplies. Through the data obtained, the water management authority would be better informed on the professional way to site, drill and manage the boreholes to avoid dry wells that leads to water scarcity.