Hydrogeological characterization of weathered and fissured basement aquifers of the Olezoa watershed in Yaoundé, Cameroon
The ground water of the altered and fissured basement of the Olezoawatershed in Centre-South Cameroon provides water to its surroundingpopulation. However, the hydrogeological characteristics of thesebasement aquifers have not yet been well studied. The present study isan attempt to better comprehend the structure and functioning of thesebasement aquifers. It mainly focuses on the description of soilprofiles, structural investigations, as well as hydrometric andpiezometric follow-ups. Preliminary results indicate that the soilprofile is of a polyphase type similar to others observed in otherparts of the world, particularly those developed on granito-gneissicformations, exposed to weathering and erosion. This is an ancientweathering system (10-20 m thick) derived from the degradation oflateritic systems and a more recent weathering (2-3 m thick) developedon the fresh rock. In addition, the profile contains alterationmicroreliefs, the spatial distribution of which can locally influenceflow dynamics. These dynamics are similar to those that commonly occurin basement rocks under wet tropical climates. The hydrometric andpiezometric characteristics indicate that the aquifers are quiteheterogeneous in some areas. The old structural tectonics control theorientation of the drainage pattern. As such, the nature of thelandscape designated by the drainage pattern is at the origin of thegroundwater flow from the upstream towards the downstream. Thedistribution of water flows from the upstream to the downstream showsthe possible influence of physical and hydraulic properties of theaquifer up-gradient from the well. This study is a contribution to theunderstanding of structures and the hydrodynamic functioning ofbasement aquifers. It shows a structural relationship with otheraquifers in other parts of world and the regional specificities whichinfluence the hydrodynamics in the weathered and fissured basement.