Intergrated Use of Geo-Electric Resistivity Sounding and Hydrogeologic Investigations for Groundwater Resource Development around Obu-Okpella South-Western Nigeri (original) (raw)

2017, IOSR journal of applied geology and geophysics

An integrated use of geo-electrical resistivity soundings and hydrogeologic methods were employed in the investigation for groundwater resource,evaluation and development around Obu-Okpella, nearBuacement factory, Southwestern Nigeria. The study area is underlain by Basement Complex rocks which consist of migmatites, granite gneiss and pegmatites.A total of 35 vertical electric soundings (VES) and four exploratory boreholes were carried out in the study. The geo-electric resistivity sounding datawere interpreted using IXD interpexsoftware and the VES interpretation revealed 4 geo-electric layers/lithologic units from the geo-electric parameters. The geo-electric layers are-(1) Topsoil from 0 to 2.5m, (2) weathered basement from 3.3 to 49m, (3) Slightly weathered/Fresh basement from 5m to ∞, (4) Fractured basement (≥5 to 150m) and are characterised by resistivity value range of 14 to 297 ohm-m, 16 to 98 ohm-m, >1000 ohm-m and < 50 to 31056 ohm-m respectively. Four exploratory boreholes numbered BH1, BH2, BH3, and BH4 were drilled on VES 1, 17, 18 and 31 to a depth of 180, 150, 58 and 110m respectively. The VES interpretation and boreholelithologic logs were well correlated. The main aquifer is in the deep and highly fractured basement rocks with average depth of 50-150m. The pumping test results for the boreholes number BH1, BH2, BH3 and BH4 were 0.8l/s, 1.87l/s, 1.2l/s and 1.7l/s respectively with very maximum dynamic water level of <10m.Transitivity value of the aquifer for BH1, BH2, BH3 and BH4 are 2.58m 2 /day, 21.43 m 2 /day, 55.62 m 2 /day, and 37.98 m 2 /day respectively indicates that the lithostrata constituting the aquifer is fair in transmitting the groundwater. With a volume of 12,000 l/day, 97,000 l/day, 91,000 l/day and 51,840 l/day for BH1, BH2, BH3 and BH4, the total volume of water for the four boreholes is 253,560 l/day.