Remote sensing and geophysical methods for delineating groundwater resources in schists hard rocks of the Adamawa Yadé Domain, Cameroon

Abstract

The combination of remote sensing and geophysical techniques is a practical approach for mapping environmental hydrogeological setting and delineating groundwater zones. This paper applies an integrated approach to identify and extract the subsurface structures that act as conduits for the groundwater flow in the highly deformed area of the Adamawa region. Remote sensing data through the lineament’s extraction technique highlights topographic lineaments along which rivers flow in the area. The distribution of these lineaments according to the lineament density map indicates the degree of permeability or porosity of each region and thus the capability in terms of groundwater potential. The filtering of aeromagnetic data enables to produce a structural map showing various geophysical lineaments interpreted as the fault systems of the study area. These faults are the main conduits through which magnetized rocks of granitoid type intruded into the basement and groundwater flows to the subsurface. Local application of the vertical electrical sounding (VES) shows that the study area is highly fractured/faulted and composed of multiple lithologic units including two aquifer layers (clayey sands and fractured schists) with thickness ranging from 5 to 15 m and from 34 to 82 m, respectively. Geoelectric cross-sections reveal that the subsurface structures consist of horsts, followed by a progressive subsidence depicted by the NE-trending faults towards the southern depression and grabens bounded by NW- and NE-trending normal faults. These prominent structures (faults, fractures, and grabens) are considered as the conduits for the groundwater flow into hard rock aquifers of the study area.