Water resources are scarce in many parts of the world, often the only supply being groundwater. Without sufficient recharge rapid decline in available levels will follow. Groundwater quality is also threatened by pollution, the effects of which will be long-reaching for generations to come. Isotopic tracing can be indispensable for solving problems such as the identification of pollution sources, evaluation of recharge and evaporation and study of interrelationships between surface and groundwater. This report discusses all aspects of this method of approaching water-related problems.