SUMMARY
The Upper Bandama watershed is drained by two major rivers: the Bandama and the Marahoué. At the zone of convergence of these affluents, an unusual behaviour of water flow regime is observed. Namely, water flow decreases from Marabadiassa to Kossou while the flow on the Marahoué increases from Zuénoula to Bouaflé. Significant volume decrease amounting to about 1 billion cubic meters is observed on the Bandama from Marabadiassa to Kossou while half a billion cubic meters of water is gained on the Marahoué from Zuénoula to Bouaflé. Dominant linear geologic fractures in NW-SE and NE-SW directions have been mapped using SPOT imagery. The fracture network is presumed to sustain underground water flow from the Bandama towards the Marahoué. The observed directions of the affluents of the river Bandama highlights a relationship between surface and underground water flow, which may regulate aquifer characteristics.