Impacts of Climate Variability on Infiltration and Groundwater Recharge in the Southeastern Coastal Region of Côte d'Ivoire

This study assesses the impacts of climate variability on infiltration and groundwater recharge within the southeastern coastal corridor of Côte d'Ivoire, spanning from Abidjan to Aboisso. The methodology integrates the Pettitt test to detect rainfall stationarity breaks, followed by water balance modeling using the Thornthwaite and Tixeront–Berkaloff methods to quantify infiltration. The analysis relies on a multi-decadal meteorological dataset, including a 54-year rainfall series (1960–2014) and a 43-year temperature record (1971–2014), coupled with a 23-year historical groundwater level monitoring dataset (1982–2005) obtained from deep boreholes. precipitation fluctuations were correlated with piezometric level variations across 30 shallow wells and 9 deep boreholes. The results identify a critical regional rainfall break occurring in 1982. Annual infiltration available for aquifer recharge ranged from 0 mm to maximum values of 856 mm, 998 mm, and 1011 mm at the Adiaké, Abidjan-Airport, and Bingerville synoptic stations, respectively. Prior to the 1982 break, mean infiltration rates (456 mm, 437 mm, and 378 mm, respectively) exceeded runoff (300 mm, 292 mm, and 285 mm), accounting for over 55% of the total rainfall surplus (infiltration + runoff). Post-1982, infiltration significantly decreased, dropping to between 20% and 40% of the surplus. Consequently, piezometric heads in deep aquifers (30 to 90 m depth) declined by 1.3 to 5.3 m, with borehole recharge occurring exclusively when the preceding year's rainfall exceeded 1,750 mm. In contrast, shallow wells (water table depth: 0.45 to 12.46 m) exhibited near-instantaneous recharge responses following rainfall events. Beyond quantifying volumetric variations, the scientific implications of these findings highlight a structural transition in the regional hydrological regime. The climate-driven reduction in natural infiltration, amplified by land surface modifications, compromises the long-term sustainability of the unconfined sedimentary aquifer system, posing severe constraints for future water resource planning in West African coastal zones. "