Time-lapse electrical resistivity investigation of seawater intrusion in coastal aquifer of Ibeno, Southeastern Nigeria

Abstract

Saltwater intrusion, erosion, and periodic flooding during severe storms are some of the critical problems bedeviling the precarious coastal environment of Nigeria. A time-lapse study aimed at monitoring the dynamics of saltwater intrusion within the coastland surrounding Ibeno, southeastern Nigeria is presented. Three (3) vertical electrical soundings (VES) and four time-lapse electrical resistivity tomography (ERT) profiles with minimum and maximum electrode spacing of 5 m and 40 m and profile lengths of 120 m and 150 m respectively were acquired in 2016 and 2017 using the Wenner and Schlumberger arrays. Data acquired from the field surveys were modeled with WINRESIST and RES2DINV software to generate 1D and 2D resistivity images of the subsurface. The VES results with a maximum survey length of AB = 300 m revealed a four-layer KH curve. The 2D geo-electrical sections delineated contrast between the high resistivity values obtained for the saturated freshwater zones and the low resistivity values obtained for the saturated saltwater zone. Expectedly, the intrusion was dominant nearer the coastline than inland. The salinity changes are believed to have been caused by both incremental tides passing through highly porous materials in the active-salinity change area and over-pumping of groundwater. The time-lapse resistivity measurements showed significant, active lateral salinity changes rapidly intruding the freshwater aquifers. The study demonstrates the application of time-lapse 2D ERT and vertical electrical sounding in identifying the spatial and temporal changes of saltwater intrusion in the coastal aquifer.

Detection and Delineation of Lateral and Vertical Extent to Fresh-Saline Water Boundary: Recent Development in Badagary Axis of the Dahomey Basin, Nigeria

“…In Nigeria, this challenge has affected over 1000 km of the coastline of Nigeria extending from Rivers and passes through Bayelsa, Akwa Ibom, Cross Rivers State, Delta, Ondo, Ogun and Lagos States, all of which share their southern border with the Atlantic Ocean and has been reported in several literatures. [Adeyemo et al, 2017[16]; Ohwoghere-Asuma, and Oghenevovwero 2017 [17]; Oloruntola et al, 2019[18]; Yusuf et al, 2021[19]; Atuluchukwu et al, 2022 [20]; A ah et al, 2018 [21]; Edet 2017 [22], Akerele et al, 2023[23], Inim et al, 2020 [24], Obunadike et al, 2024 [25]]. The works of Oteri and Atolagbe (2003) [26] reported that salt water incursion has been occurring especially in coastal areas of the Niger Delta, Nigeria.…”

Integrated valorization of MSW incursion into water resources: a tool for environmental monitoring and assessment near dumpsite areas, Akwa Ibom State, Nigeria

“…Geo-elect rical t echnology and geochemical assessment have been proven t o be sensit ive in valorizing t he channel of leachat e plumes in bot h t he surface and groundw at er resources (George et al, 2023). Through t his t echnique, many researchers have used geo-elect rical t echnology involving 1D and 2D t echniques t o validat e t he effect of leachat e on groundw at er t hrough t he monit oring of groundw at er conduct ivit y or resist ivit y Inim et al(2020) have used elect rical resist ivit y t ime lapse t o ident ify t he rat e of infusion of leachat e in groundw at er resources and t he result s show ed t hat t he vert ical and horizont al percolat ion of leachat e from t he source t o t he cont iguous environment increases w it h t ime. Inim et al (2020) also ut ilized bot h t ime lapse geo-elect rical t echnology employing 1D and 2D conventional curve matching method (CMM) approaches and physiochemical (in sit u and laborat ory) measurement s and assessment s t o show t hat leachat e plumes lead t o an increase in groundw at er conduct ivit y and a decrease in groundw at er resist ivit y.…”

“…Through t his t echnique, many researchers have used geo-elect rical t echnology involving 1D and 2D t echniques t o validat e t he effect of leachat e on groundw at er t hrough t he monit oring of groundw at er conduct ivit y or resist ivit y Inim et al(2020) have used elect rical resist ivit y t ime lapse t o ident ify t he rat e of infusion of leachat e in groundw at er resources and t he result s show ed t hat t he vert ical and horizont al percolat ion of leachat e from t he source t o t he cont iguous environment increases w it h t ime. Inim et al (2020) also ut ilized bot h t ime lapse geo-elect rical t echnology employing 1D and 2D conventional curve matching method (CMM) approaches and physiochemical (in sit u and laborat ory) measurement s and assessment s t o show t hat leachat e plumes lead t o an increase in groundw at er conduct ivit y and a decrease in groundw at er resist ivit y. How ever, t he w ork carried out by t he researchers ident ified did not consider t he generat ion of leachat e plume dist ribut ion pot ent ial maps, w hich can indicat e t he dow nst ream, midst ream and upst ream of leachat e plume direct ions for efficient environment al monit oring and assessment .…”

Characterization of a marine intrusion using electrical sounding and seismic refraction: case of the the Oued Nador plain (Tipaza, Algeria)

“…As a result, a large part of Algeria's population is dependent on coastal water resources and for the majority on groundwater resources. In addition, high water demands occur during the summer season, when groundwater levels are at their lowest (Comte, 2008;Moulla, 2013;Cocheril, 2019;Inim, 2020).…”