The global production of food, notably cereal crops, appears to have been remarkably resilient to the vagaries of climate. The unsung hero in this production chain may well be groundwater. When rainfed agriculture fails, the fallback is usually groundwater. First it is accessed to smooth over the dry periods, and then it becomes a habit. Therefore, staying within strict resource limits would seem to be the obvious piece of management advice. That sensible advice was given in the late 1950s; in the meantime the green revolution occurred and 40 years later the resource limits on many key aquifers have been exceeded. High-quality groundwater that had taken thousands of years to emplace has gone in a few decades, leaving agriculture, municipalities and rural communities competing for the recoverable groundwater that remains. This paper explains why conventional approaches to groundwater management may need to be re-thought.