IMPACT OF PUMPING REGIME ON THE RECHARGE BALANCE OF THE CONTINENTAL TERMINAL AQUIFER OF THE ALLADA PLATEAU: CASE OF THE GODOMEY AND OUEDO WELLS IN THE COMMUNE OF ABOMEY-CALAVI (SOUTHERN BENIN)

The continental terminal aquifer is the main hydrogeological formation used to supply drinking water to the population of southern Benin. This study examines the impact of the intensive pumping regime of the Ouedo and Godomey wells on the recharge of the continental terminal aquifer in the municipality of Abomey-Calavi. The methodological approach is based on a comparative analysis of pumping tests between two periods, 2001 and 2023, using the OUAIP software; a model of natural recharge over the period 2011-2025 using the ESPERE tool (groundwater fluctuation methods and the Turc method) with an effective porosity of 0.26 obtained from previous studies in the area; and a statistical forecast estimate based on linear regression line equations intersecting the population growth of the INSTAD (National Institute of Statistics and Aquatic Environments) and the historical volumes of water pumped by SONEB (National Water Company of Benin). The results show a decrease in the hydrodynamic properties of the continental terminal due to intensive pumping. Indeed, the average transmissivity decreased between 2001 and 2023. Concurrently, the storage coefficient increased between 2001 and 2023, reflecting localized deconfinement.