Assessment of Groundwater Potential of Imo Formation (Ebenebe Sandstone) in Anambra State, Nigeria Using Geo-electrical Sounding Data

Abstract

Failure of public water scheme and adverse pollution of surface water sources have made residents of Anambra State to resort to groundwater resource. The objective of this study is to provide data on groundwater prospect considering the subsurface geophysical conditions of Imo formation (Ebenebe Sandstone) to enhance the availability of clean water source. Vertical Electric Sounding (VES) method was used for this study by measuring 15 VES stations using Schlumberger configuration. The results revealed thatthe subsurface section consists of five geo-electrical layers namely: Top soil/laterite, Clayey sand, Dry sandstone, Water saturated sand and Shale. The predominant curve types found in the formation were AK, HK and K. The first layer encountered had depth that ranges from 2.94 to 5.21m, thickness of 2.94 to 5.21m, with resistivity values ranging from 278 to 1959.96 Ohm.m. The second layers thickness and resistivity values for all the VES stations ranged between 13.38 – 23.66m and 304.12 - 909.7Ωm respectively, this layer was delineated mainly as clayey sand. The third layers were delineated mainly as sandstone; the thickness and resistivity ranged between 26.53 – 68.89.89m and 7548.4 – 14026.15Ωm respectively. The depth of the third layer varied from 44.44m to 88.72m. For the forth layers, the thickness and resistivity ranged between 18.73 – 43.96m and 13499.1 – 4620.14Ωm respectively and they are delineated mainlyas water saturated sand for all the VES stations. The fifth/last layers bases were not reached, the values of their resistivity ranged between 29.663 – 60.41Ωm and they were delineated as shale.