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

The Continental Terminal aquifer is the main hydrogeological formation exploited for the supply of drinking water to the populations of southern Benin. This study evaluates the impact of the intensive pumping regime of the Ouèdo and Godomey wellfields on the recharge of the Continental Terminal in the Municipality of Abomey-Calavi. The methodological approach is based on a comparative analysis of pumping tests (2001-2023) using the OUAIP software, a modelling of natural recharge over the period 2011-2025 using the ESPERE tool (Water Table Fluctuation and Turkish methods) using an effective porosity of 0.26, as well as a statistical forecast estimate based on linear regression line equations cross-referencing the demographic evolution of the INSTAD and the historical of SONEB levies. The results show a decrease in the values of the hydrodynamic properties of the Continental Terminal under the effect of intensive pumping. Indeed, the average transmissivity has dropped from 7.97〖.10〗^(-3) m^2/s in 2001 to 2.22.〖.10〗^(-3) m^2/s in 2023. At the same time, the storage coefficient increased from 〖.10〗^(-9)in 2001 to 〖2.33.10〗^(-3) in 2023, reflecting a localized deconfinement and a shift from captive to semi-captive or free behavior. The Godomey wellfield alone is undergoing an average intensive extraction rate of 47,000 m³ per day, bringing annual withdrawals to 34 million m³ for a population served that already reaches 1.3 million inhabitants in 2025. The application of the equations of regression lines shows a strict linear correlation between population growth and the artificial discharge of the water table. Mathematical projections for 2040 establish that the population will reach a critical 1.95 million inhabitants, propelling the need for drinking water and the volumes withdrawn from the Godomey field to an estimated level of 58.3 million m³/year. Faced with the threat of widespread drying up, regulation of operating flows coupled with urgent artificial recharge actions is essential. Keywords: Continental Terminal, Evolution, Wellfield, Benin, Overexploitation