An SP survey for groundwater and correlation with Resistivity survey results in parts of Mbano area of Imo State, Nigeria.
By Leonard I. Nwosu, Cyril N. Nwankwo and Anthony S. Ekine
Seventeen vertical electric soundings covering about 196 square kilometer area of Isiala Mbano in Imo State, Nigeria were carried out in this study during which apparent resistivity and SP data were simultaneously measured using the Schlumberger electrode array. The contour map of the study area shows the distribution of equipotential lines across the area. The results show high SP anomaly value of 284 mV around Ezumoha (VES 15) in the northern part, 213 mV at Umuechem (VES 1) in the western part and 197 mV around Ogbor (VES 9) in the southern part. These are areas of favourable aquifer. They form the discharge zones with strong lateral flow, having high aquifer thickness and transmissivity as revealed by resistivity survey. Low SP anomaly was obtained with troughs around Obiohuru, VES 5 (-19 mv), Umuneke, VES 13 (-116mV) and Umunkwo VES 3, (-120mv). These correspond to areas of infiltration.
The result of Self Potential (SP) method of prospecting was correlated with Resistivity survey for regional detailed quantitative work of the study area. SP survey correlated well with that of resistivity survey in the study area, with the depths to aquifer calculated from SP sounding curves matching very closely with those obtained from resistivity curves in most of the 17 sounding stations. The cross-correlation coefficient computed for each pair of depths gave correlation significance at 1%, which validates the results.
Key words: Correlation, groundwater potential, SP survey, resistivity
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