Climate change is intensifying water-related extremes, exposing communities to devastating floods and prolonged water shortages. Yet beneath our feet lies an often-overlooked opportunity: aquifers can capture and store freshwater when it is abundant at the surface. Drawing on research in Bangladesh, Tanzania and Niger, this lecture explores how groundwater abstraction and seasonal flooding can enhance aquifer replenishment and strengthen water and food security. The Bengal Water Machine illustrates this potential while also revealing important environmental trade-offs. The lecture challenges conventional narratives of groundwater depletion and asks how we can harness nature’s underground storage more sustainably in a changing climate.