Integrated geophysical and remote sensing/GIS interpretation for delineating the structural elements and groundwater aquifers of the Foumban locality, Western Highlands of Cameroon (WHC)

Abstract

• Five main families of lineament directions following the Cameroon Volcanic Line. • The alternate materials are discontinuous and heterogeneous. • Alternate layers of conductive, semi resistive and resistive formations. • Locating appropriate positions of new productive wells in the study area. This study was conducted in the Foumban locality, in the Western Highlands of Cameroon (WHC) where a majority of the population is suffering from scarcity of water for domestic purposes and many other related uses. Thus, it aims at investigating the structural and geo-electrical characteristics of the aquifer system of the locality, based on an integrated approach (Geophysics and GIS). For this purpose, the Landsat 8 image with 30 × 30 m resolution and 20 vertical electrical sounding (VES) data were analysed with ArcGIS, ENVI version 5.3 , Stereonet v9.3.2 and QWSELN software, coupled with the principal component analysis (PCA). Based on the structural aspect, a total of 224 fractures with lengths higher than 1 km have been identified and drawn. They are mainly grouped in the Centre, North-East and South-East of the study area. Five main families within linear directions have been identified: N10-20 (13.84%), N20-30 (17.86%), N50-60 (9.82%), N80-90 (5.90%) and N140-150 (7.59%). They are mostly oriented NE-SW, following the Cameroon Volcanic Line (CVL). These fractures which play an important role in the capacitive and drainage function of the fractured aquifer result from the tectonic movements and decompression of rock masses. According to the geoelectrical characteristics, different VES curve types have been identified, corresponding to various alternate layers of conductive, semi resistive and resistive formations; with thickness ranging between 0.41 to 47 m and resistivity values between 82 to 3410 Ωm. The three cross-section realised (A-A’, B-B’ and C-C’) show that those alternate materials (topsoil, laterite, weathered layer, fractured basement and fresh basement rock) are discontinuous both vertically and horizontally, highlighting the geometry and hydrogeological complexity of these areas. This study is a contribution to a better understanding of the basement aquifers milieu; it could be used by the water supply departments and decision makers for locating appropriate positions of new productive wells in the study area.