Tectonical-pattern of Basement Aquifers: New Insight from Combined Analysis of Wells and Electrical Resistivity Data of Bertoua Area, East Cameroon

Abstract

ABSTRACT Groundwater is the main source of water for the population of the town of Bertoua (East Cameroon). However, most of the waterworks that have been built are characterized by low flow rates, which generally lead to dewatering. The aim of this study is to identify and locate the different types of aquifer in the Bertoua region and determine the influence of tectonics on their characteristics. To achieve this, satellite images and vertical electrical soundings (VES) were used. The major orientations of the lineaments highlighted are N030-060 (NE-SSW), N105-135 (ESE-WSW), and N345-10 (N-S). These directions represent 27, 12, and 9%, respectively, of the lineaments interpreted. The vertical electrical boreholes are characterized by four types of curves: KH, AK, HA, and A. The aquifer levels have resistivities between 86 and 1540 Ω m. These levels are located at a depth of 4.50–45 m. The thickness of the water table varies from 5 to 42 m. Flow rates range from 0.54 to 9.80 m3/h. The correlation between the borehole data, the geoelectric data, and the characteristics of the existing boreholes shows that the KH and AK type curves have the best hydrogeological potential. These are characterized by the presence of alterite aquifers and fracture aquifers. Those of type A have the lowest potential and are not very recommendable. The nature of the geological formations seems to play less of a role in borehole productivity. The direction of the lineaments, on the other hand, plays a key role in the productivity of these boreholes. The NE-SW direction, perpendicular to the flow of the watercourses, is the most productive, while those parallel (N-S) present less interesting potential. The model presented here is characterized by the variation in the number of terrains within the same direction. It can only be applied to areas with same geological and tectonic context and which have been affected by the same external geodynamic processes.