Rising threats to groundwater recharge: Adaptive strategies for the Sahel under climate change

Groundwater recharge is a fundamental pillar of water security in arid and semi-arid regions, particularly in the Sahel, where climate change is driving profound hydrological shifts. This review critically synthesizes current knowledge on the interplay between climate variability and groundwater recharge dynamics, addressing the following research question: How do different climate and human-induced factors impact groundwater recharge in the Sahel, and what strategies can enhance resilience? The review emphasizes the impacts of shifting precipitation regimes, rising temperatures, and increasing evapotranspiration rates. Observed trends indicate a contraction of rainy seasons, greater rainfall intermittency, and rising temperatures, key drivers that exacerbate groundwater stress. Comparatively, land use changes and water governance structures also influence recharge patterns, but to a lesser extent. These climate and anthropogenic shifts have made recharge processes more episodic and spatially heterogeneous, complicating sustainable groundwater management. Projections suggest these trends will continue, further straining groundwater resources. The review examines the role of localized factors, such as land use changes, soil characteristics, and governance frameworks, in modulating recharge variability. Through regional case studies, it highlights challenges in data-scarce environments and the need for more refined climate-hydrology models. To address these emerging threats, the review explores adaptive strategies, including Managed Aquifer Recharge (MAR), rainwater harvesting, and advanced hydro-technological innovations. The critical role of governance and policy frameworks is also discussed, with an emphasis on transboundary cooperation, integrated water management, and locally informed decision-making. Despite these advancements, significant research gaps remain, particularly in long-term groundwater monitoring, predictive climate modeling, and interdisciplinary approaches. By bridging these gaps, this review provides a scientific foundation for adaptive groundwater management in the Sahel, offering insights essential for ensuring long-term water security and resilience in one of the world's most vulnerable regions.