Aquifer vulnerability and protective capacity test of Lokoja, Kogi state, North-Central Nigeria

The aquifer vulnerability test seeks to quantify the sensitivity of an aquifer system to groundwater degradation due to human and natural activities and shallow aquifers depth. As a result of the increasing trends in groundwater contamination, this research was carried out to determine the aquifer vulnerability of the Lokoja metropolis through IECs and GOD techniques. The IECs indices for lithologies that overlie the aquifers were computed using the interpreted layer resistivity and thicknesses. Twenty-five (25) VES stations were evaluated in which VES stations 15, 16, 17 and 18) are within the Sedimentary Basin and the remaining VES are within the Basement Complex with the vadose zone located at the second layer. VES station 5, 9 and 24 has five (5) layers and the aquiferous zone is found in the fourth layer while the remaining VES stations have four (4) layers and the aquiferous zone is found in the third layer. The Aquifers in the study area are shallow and are less than 40m deep. The IEC value observed in the area ranges from 0.02-0.56 and GOD values from 0.59-0.705 which indicates high to extreme vulnerability areas because the aquifer protective capacity is fairly weak. The aquifers exist under unconfined to partially confined conditions. The composition of the overlying materials varies from argillaceous materials to consolidated sandstone materials. Thus, the protection capacity offered by the overlying materials to the aquifer varies from weak to fair depending on the composition of the overlying materials that in many cases, depends on the paleotectonic events of the area.