Groundwater must be fully integrated into WASH programmes to make them climate resilient

Groundwater is a critical source of freshwater that provides nearly half of global drinking water. Its comparative resilience to weather and climatic extremes, particularly drought, makes it essential to water security across agricultural, industrial, and ecological systems around the world [1–4]. In the Water, Sanitation and Hygiene (WASH) sector, groundwater is the predominant source of water for WASH services, especially in rural and low, middle-income settings (LMICs). Its prominence is driven, in part, by its widespread distribution and general resilience [5]. Yet, groundwater is not only a source for WASH services but impacted by them, both from contamination and overexploitation, highlighting a complex interdependent relationship. However, despite groundwater’s fundamental importance, understanding and accounting for groundwater has long been an ‘invisible’ component in WASH programming and wider development planning – sidelined as a water resources issue instead of being core to ensuring sustainable service delivery [1,3,6]. As the WASH sector prioritizes climate resilience, this disconnect— as we noted in discussions at the 2024 UNC Water & Health Conference - is increasingly import ant to address. A recent, and welcomed, definition of climate-resilient WASH ser vices [7] highlights the need for systems that can anticipate, respond to, cope with, and recover from climate-related events. Yet how can we ensure these goals are met if the underlying water resource for WASH services is poorly understood, not accounted for, and inconsistently managed? We argue that without integration – not just coordination - of groundwater into WASH programming, the climate-resilient WASH vision risks being aspirational rather than achievable.