Spatial Distribution and Predictive Modeling of Aquifer Protective Capacity via Dar Zarrouk Parameter Analysis in the Lower Orashi River Area, South Eastern Nigeria

Abstract

Aquifer protective capacity refers to the ability of overlying geological materials to protect groundwater resources from surface-derived contamination. This study illustrates the geo-electrical characterisation of lithology and investigates the correlation between resistivity and Dar-Zarrouk parameters (transverse unit resistance and longitudinal unit conductance), aiming to assess the aquifer's protective capability. This is achieved by examining the thickness, lithology, and hydraulic characteristics of subsurface layers that influence the movement and attenuation of contaminants. Parameters such as clay content, resistivity, permeability, and depth to aquifer were considered in assessing the effectiveness of natural protective barriers. Geophysical and hydrogeological data were integrated to classify the study area into zones of poor, moderate, and good protective capacity. Areas characterized by thick, low-permeability clay or shale layers exhibit high protective capacity, while zones dominated by sandy or fractured materials with shallow aquifers show reduced protection and increased susceptibility to contamination. The Schlumberger Electrode Configuration was used to collect eighty-eight Vertical Electrical Sounding (VES) data points. The most space between the electrodes (AB/2) was 350 meters Win resist software was used to look at the VES data we got. The Alluvium, Benin, Ogwashi, and Ameki Formations make up the geological layers below the area. The study found seven to ten geo-electric layers of different rock types, such as topsoil, clay/sandy clay, and sand. The area is mostly made up of sandy formations and has a lot of aquifers, most of which are not restricted. This means that the study area have great groundwater potential and a little amount of aquifer protection. This is confirmed by drastic index map produced since most of the region we looked at is unsafe. The results demonstrate that aquifer protective capacity is strongly controlled by subsurface lithology and layer thickness, emphasizing the importance of geological conditions in groundwater protection. The findings provide valuable information for groundwater resource management, land-use planning, and the siting of potentially contaminating activities, thereby supporting sustainable use and protection of groundwater resources.