Electro-sequence valorization of specific enablers of aquifer vulnerability and contamination: A case of index-based model approach for ascertaining the threats to quality groundwater in sedimentary beds

Abstract

This work was set up to appraise the quality of groundwater within a newly established university using index-based techniques and the intention is to generate vulnerability potential maps that can guide in avoiding vulnerable aquifer systems. The study used geo-electrical technology to evaluate the lithological sequence of the hydrogeological units and their first-and second-order geo-electric properties, as well as the geochemical constituents of groundwater. The results showed that the hydrogeological units are composed of sequences of sands, including fine to gravelly sands minimally laced with sandy clay, according to the results of geo-electrical technology. Layers 2 and 3 were accessible by the twenty VES (V1-V20) in which current gained access to designated economic and prospective aquifer systems. The aquifer systems considered have resistivity values ranging from 26.3 to 3576.5Ωm and mean value of 832.97Ωm. The five vulnerability models deployed showed very high spatial variability and moderate negative and positive binary correlations, construed to be due to subjectivity in the weight-rate assignment. The coefficients of variation (CV) from sensitivity analysis (SA) indicated variation in the vulnerability index due to topography (9.7%) and the impact of the vadose zone (4.3%), which are marginally higher than the 1.6% displayed by other parameters. The groundwater displayed WHO's disallowed concentrations of heavy ions, and the SA indicated that CV for the groundwater geochemical contamination is variably high in cadmium ions (140.9%) followed by manganese ions (132%) and copper ions (88. 2%) across the wells. The moderately variable contribution distributions across the wells are nickel ions (48.8%), lead ions (41.6%), chromium ions (39.8%) and iron ions (35.0%). All the geophysical and geochemical indices affirm that the groundwater is vulnerable and contaminated and therefore requires monitoring and management.