Public water supply in Europe relies very heavily on groundwater. Recharge of groundwater takes place mainly in the winter months. An analysis of winter rainfall data shows that current recharge rates are abnormally high, and that during several periods in the past the rate has been less than half the current value. A return to such low values could have catastrophic consequences, but even more modest drops would be serious. Useful predictions must be based on climatic models and the full use of climatic, paleohydrological and historical data.