Evaluation of Aquifer Hydraulic Properties and Vulnerability Indices in Mosogar using Geoelectrical Approach

Abstract

Geophysical investigation employing vertical electrical sounding (VES), pumping test and in situ groundwater conductivity measurement  were carried out in Mosogar, Delta State in order to determine the aquifer properties and vulnerability indices. The Schlumberger  electrode configuration was used for the vertical electrical sounding (VES) survey to acquire electrical resistivity data which were  interpreted using the WinResist software, version 1.0 (2004). The results revealed that the lithology is composed mainly of sand with  various grades with four to five delineated geoelectric layers. Results of hydraulic conductivity, transmissivity and formation factor of the  aquifer were found to vary from 7.9233 to 9.2799 m/day, 45.670 – 235.323 m2 /day and 0.545 – 23.664 respectively. Aquifer vulnerability  indices within the study location indicate moderate to extremely high vulnerability as classified by aquifer protective capacity (APC),  aquifer vulnerability index (AVI), Geo-electric layer susceptibility index (GLSI) and groundwater confinement, overlying strata and  groundwater depth index (GOD) models employed, with values ranging from 0.00766 - 0.038728, -0.5631- 0.3025, 2.25 - 3.00 and 0.4 -0.8  respectively. The results revealed that the groundwater is prone to contamination because of weak protection provided by overlying  geologic units. Using the Golden surfer 10 software, maps of geo-hydraulic parameters and vulnerability indices were constructed which characterises the aquifer parameters in the area. This study provides an important tool for sustainable groundwater exploration and  management in Mosogar