Groundwater development is rising in many countries in response to demands for water and the decline in the reliability of surface water sources and rainfall.  This has led to narratives of overexploitation, breaching planetary boundaries and ultimately - crisis.   Legitimate concern on the unsustainable development of groundwater, however, is only part of the picture, and groundwater, often silently, is solving many of the current water issues presented by a growing population, unreliable public supply and a changing climate.  Drawing on examples from Africa and South Asia I present how understanding hydrogeological, climatic and societal conditions can throw light on past and future trajectories of change, and highlight the opportunities for groundwater development as well as the threats.

For example, in sub-Saharan Africa crystalline basement aquifers  underlie much of the populated areas, and sustain many rural water supplies.  The low permeability aquifer often sustains small rural water supplies with appropriate investigations, but inherently self regulates against much larger supplies which could deplete wider areas of the aquifer.  There is also growing evidence that groundwater development can increase recharge, and that changes in modalities of rainfall may favour groundwater recharge.  At the other end of the scale, water insecurity caused by unreliable city municipal supply is often mitigated by private wells run by individual households and also private enterprise.  Such supplies are plugging a supply gap and enabling cities to grow. 

In South Asia, where groundwater development is well advanced the situation is very different with high abstraction for irrigation widespread.  Examples from India and Pakistan show that the construction of canals for surface water irrigation fundamentally changed the hydrogeology:  increasing groundwater recharge and raising groundwater levels throughout the 20^th century.  High groundwater abstraction is now impacting groundwater levels and baseflow to rivers, with groundwater levels reducing in many areas.  However, climate variability, abstraction, irrigation and current and future glacier melting is also having an impact on groundwater recharge which means that groundwater storage is not universally declining.

This richly complex situation means there is much room for optimism and intervention to increase sustainability of abstraction, and to help refocus on the arguably greater and more immediate threat of deteriorating water quality.