Geophysical Investigations and Aquifer Characteristics of the Benin Formation at Agbarho, Delta State, Nigeria

Groundwater investigations were carried out at Agbarho using geophysical survey method to delineate the aquifer and subsurface lithology. Three (3) vertical electrical sounding were conducted with a maximum current electrode spacing of 300m. The data acquired were subjected to partial curve matching and computer processing. The results delineated five geoelectric layers for the area, which include; topsoil, silty sand, silty clay, fine sand, medium grain sand and coarse sand. The Dar-Zarrouk parameter revealed an aquifer system that has a resistivity values ranging from 503.9-966.9ohm-m, an average hydraulic conductivity of 7.73 m/day, and transmissivity in the range of 156.24-181.44m2/day. The depth to the aquifer range from 13.2-42.7m and the aquifer thickness is between 7-36.7m. Results from seven down-hole logs revealed the presence of silty sand, fine sand and fine-medium grained sand. The transmissivity values from pumping test range from 162.29-286.56m2/day and storativity is from 0.001-0.00838. The aquifer is capable of yielding useful quantity of water to the wells and sustainable groundwater management plan can be develop for the area.