Characterization of aquifer vulnerability in parts of the western Niger Delta

• Published in: Arabian journal of geosciences 2024, Vol.17 (2), Article 66
• Main Authors: Mgbolu, Chinedu Charles, Obiadi, Izuchukwu Ignatius, Opuh, Chukwuma Kingsley, Emeh, Chukwuebuka, Irumhe, Emmanuel Paul, Mbagwu, Adaeze Chizaram, Anene, Chibundu Zimuzo
• Format: Article
• Language: English
• Subjects: Aquifers; Boreholes; Contaminants; Contamination; Depth; Direct current; Earth and Environmental Science; Earth Sciences; Electrical resistivity; Geology; Groundwater; Groundwater management; Hydrogeology; Lithology; Original Paper; Sandstone; Sedimentary rocks; Shale; Unconsolidated aquifers; Vulnerability; Water depth; Water resources
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-024-11867-x

Aquifer characterization is essential for groundwater sustainability in the Niger Delta region. The unconsolidated aquifers of the region are sandy and porous, and have the potential to allow the passage of contaminants to the groundwater resource. The first-order geo-electric parameters of the subsurface, procured by injection of a direct current into the ground were applied to evaluate the aquifer vulnerability in the region. The Schlumberger architecture was engaged to acquire vertical electrical sounding (VES) data at different points and processed using Interpex 1D™. Electrical resistivity imaging (ERI) using a multi-electrode Wenner-α array was also applied across the study area and constrained with existing borehole data to establish the accuracy of the VES results. The VES result revealed the occurrence of 5 to 6 geo-electric strata across the region. The rock types identified from the VES result and ERI pseudo-section were mostly sandstone intercalated with shale and clayey sand at some points. The result also revealed that the depth to water-bearing formation within the area is relatively shallow with aquifer depth values ranging from 7.7 to 103 m and thickness of the aquifer varies from 4.7 to 149.7 m, while the aquifer resistivity values ranged from 470.84 to 2697.7 Ωm. The aquifer protective coverage (APC) assessment revealed that the study area has weak and poor protective covers, while the geo-electric layer susceptibility indexing (GLSI) shows that the area is characterized by low and moderate vulnerability status. The GOD index measurement across the area also revealed that the area has low and average vulnerability status at different points. GOD represents an acronym for three hydrogeological factors, and they are confinement of the aquifer (G), overlying lithology of the aquifer (O), and depth to the aquifer (D). The poor and weak protective covers which gave rise to the low and average vulnerability are indicators that the aquifers within the region are prone to contamination from surface sources. This research is vital for groundwater management and contamination assessment in sandy aquifers.