Book excerpt: Providing an introduction to the crucially important topic of groundwater, this text covers all major fields of hydrogeology and includes outlines of the occurrence of groundwater in various rock types, the movement and storage of groundwater, the formulation of groundwater balances, the development of groundwater chemistry, as well as the practical application of hydrogeology for groundwater development. Following a unique systems approach to describe and connect its various elements, the text also explores a large selection of examples of groundwater cases from various parts of the world. In addition, theoretical sections and examples are illustrated with a number of drawings, photos and computer printouts. Suitable for education in hydrogeology at postgraduate and graduate level, the text is also a useful reference tool for professionals and decision-makers involved in water or water-related activities. In the revised paperback edition of Introduction to Hydrogeology (February 2006), suggestions of reviewers, students and collaegues have been taken into account. This means that more attention is paid to the processes in the unsaturated zone, especially those relating to groundwater recharge. Also, in the revised edition, the investigation methods are highlighted in the sections where the related theory is dealt with, and they are not presented in the last chapter on groundwater management. Chapter titles are re-named and some definitions are adjusted. The References and Bibliography section is also extended, some figures are improved, and the unevitable ‘typing errors’ are corrected as well.