Characterization of formations and groundwater potential of Amai and Obiaruku in Delta State using resistivity and seismic refraction measurements

Abstract

Obiaruku and Amai are two communities with remarkable high population due to their nearness to flowing waters which is one of the bases of early settlements. Although, the two towns are only 3 kilometres apart their geological and geophysical presentations vary remarkably. While Obiaruku is flanked by the early stage of the fast flowing North - South fresh-water river Ethiope, Amai has slow flowing filthy stream which spreads out and sometimes over flows its bank. Moreover, while Amai has numerous hand dug wells which are filled up to 2.5 metres or less depending on the season under investigation, Obiaruku has no evidence of hand dug well all the year round. The disparities in presentations are of interest. It becomes necessary to carryout a geophysical investigation of the formation strata and groundwater potential for the ever growing population of these communities. Hence a characterization of the formations and groundwater distributions were carried out using Schlumberger array of electrical resisitivity and up-hole shooting of seismic refraction surveys. Twelve Vertical Electrical Sounding (VES) stations were sounded using Self Averaging System SAS ABEM 300C tarrameter and eight refraction sounding sites were shot using Seismograph OYO MESEIS 160mx. The study shows that while Obiaruku has QA and HA curve types, which have basically four or more distinct resistive layers, Amai consists of A-type curve which has mainly three or four distinct resistive layers. The soil formation in Amai is highly conducting clay while that of Obiaruku is mainly laterite. Moreover, while Groundwater is at 45 – 50 m depth in a region of unconfined aquifer at Obiaruku, it is as low as 20 m in a zone of confined aquifer at Amai.

Journal of the Nigerian Association of Mathematical Physics Vol. 10 2006: pp. 83-90