Chapter 1. Introduction -- Part 1. General Hydrology -- Chapter 2. Heories and basic terminology -- Chapter 3. Voids in the subsoil -- Chapter 4. Geohydraulics -- Chapter 5. Surface water infiltration -- Chapter 6. Groundwater Dynamics -- Chapter 7. Ground water Morphology -- Chapter 8. Hydrological cycle – water balance -- Chapter 9. Numerical Groundwater models -- Chapter 10. Basic Physical and Chemical Factors -- Part II. Groundwater Properties -- Chapter 11. Basic chemical and physicochemical principles -- Chapter 12. Physicochemical processes in groundwater flow -- Chapter 13. Ground water Fauna: Biology -- Chapter 14. Ground water classifications. Part III. Applied Hydrogeology -- Chapter 15. Ground water exploitations -- Chapter 16. Geohydraulic investigations -- Chapter 17. Water exploitation -- Chapter 18. Chapter 19. Building-area ground damage due to groundwater abstraction.This textbook provides a complete introduction to Hydrogeology. It is a comprehensive reference for earth science professionals involved in groundwater exploitation as well as for geotechnical engineers. This English translation of the German textbook "Hydrogeologie" by Hölting & Coldewey, which has been published in its 8th edition, provides insights into the sources and reservoirs of groundwater, the dynamics of fluid flow, and the physical and chemical composition of groundwater. It also gives an overview about the economic value of groundwater and its exploitation and use. A consistent use of the internationally accepted SI units as well as the formula symbols in the text contributes to the understandability. .