IMPACTS DES CHANGEMENTS CLIMATIQUES SUR LES EAUX SOUTERRAINES DES AQUIFERES DE SOCLE CRISTALLIN ET CRISTALLOPHYLLIEN EN AFRIQUE DE L’OUEST: CAS DU BASSIN VERSANT DU N’ZI-BANDAMA (COTE D’IVOIRE)

Abstract

The objective of this study is to evaluate the impacts of climate change on groundwater resources of crystalline and crystallophyllian basement aquifers. This study was applied to the particular case of N'zi-Bandama watershed in Ivory Coast. This catchment lies between longitudes 3°49' and 5°22' West and latitude 6°00’ and 9°26' North and covers an area of 35,500 Km2. It belongs to three climatic regimes that are from North to South, the tropical transition regime, the humid tropical regime and sub-equatorial regime. The main geological formations of the basin are granites, migmatites and granodiorites. There are two types of aquifers that are the regolith aquifers and fissured aquifers. The methodological approach is based on the evaluation of recession coefficients, of the dry period and the water volume mobilized by the aquifers. All these parameters were estimated from the law of Maillet. The recession coefficients estimated average between 3.14.10^-2j^-1 and 3.56.10^-2 j^-1 either side 1968, whether an average increase of 15.26% and highlight a drain much faster aquifers supplying base flow after 1968. Shortening of 1 to 9 days with an average of 5 days of drying time after 1968 was highlighted. The water volume mobilized by the average aquifer fluctuates between 0.84 and 0.42 Km³ before and after 1968 whether an average decrease of -49.3%. These results show a decrease in the water volume mobilized by aquifers after 1968 and suggest a considerable decline of groundwater resources under the influence of climate change.