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.
Key words: Vulnerability index, GOD model, geo-hydraulic parameters, Formation Factor, Aquifer
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