MAPPING OF SALTWATER INTRUSION AT IGBOKODA, SOUTHWESTERN, NIGERIA USING COMBINED GEOPHYSICAL AND CHEMICAL TECHNIQUES

James Adegoke,Emmanuel Adetuwo,Wilfred Igboama

doi:10.29081/jesr.v24i1.62

Abstract

This research work was set out to map saltwater intrusion in Igbokoda area of Ilaje, Ondo State, Southwestern, Nigeria using combined geophysical and chemical techniques. Eight (8) Vertical Electrical sounding were carried out using the Schlumberger Electrode array system with maximum spread of (AB/2) 133 m and water samples were acquired and analysed using atomic absorption spectrometer. The VES data was interpreted by the method of partial curve matching and computer iteration technique using Winresist software. The result obtained revealed four geoelectric layers. The saltwater intrusion originated from movement of seawater into the freshwater aquifer coupled with human activities.

Highlights

Groundwater are found underground in cracks and spaces in soil, sand and rocks
Water samples collection and preparation Water samples were collected into 1 L high density polyethylene (HDPE) plastic vials pre-treated with 4M HNO3 and properly rinsed with de-ionized water followed by doubly distilled water before use
Depth Sounding Curve Types The various curve types show the qualitative interpretation of the Vertical Electrical Sounding (VES) data, two curve types were identified within the study area (Table 1): 1. KH-Type curve: This curve represents geoelectric lithologies with layer resistivity showing the following format ρ1ρ3

Summary

Introduction

Groundwater are found underground in cracks and spaces in soil, sand and rocks. The area where water fills these spaces is the saturated zone. Groundwater is stored in – and moves slowly through - layers of soil, sand and rocks called aquifers [1]. The quality and availability of these fresh groundwater resources in coastal areas are hampered by seawater intrusion from the seaside. This is a natural process, by which seawater displaces and mixes with the fresh groundwater in coastal aquifers due to the density difference existing between waters of different salinities. Saltwater intrusion i.e. the displacement of fresh groundwater by groundwater with a higher salinity has become an accepted scientific term in the research field [2]

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Conclusion