The long-awaited Second Edition of Introduction to Groundwater Hydrology presents the fundamentals of groundwater hydrology, as well as the knowledge and approaches needed to address contemporary problems in hydrogeology. The theme of the book is groundwater, broadly defined with a focus on fundamentals and problems necessary to deal with aquifer depletion and associated issues. It covers the theory and practice of groundwater from basic principles of physical and chemical hydrogeology to their application to traditional and emerging areas of practice. Thoroughly updated, the early chapters in this new edition, discuss the hydrologic cycle and associated near surface processes like infiltration, overland flow, and streamflow in the hydrologic cycle. Subsequent chapters cover theory of groundwater flow (e.g., concepts of hydraulic head, Darcy equation, etc.), ground water/surface water interactions, and unsaturated flow and fractured media. Techniques of water resources investigations and regional groundwater flow are also examined in detail. The latter part of the book focuses on problems associated with depletion of aquifers worldwide and tools and knowledge necessary for sustainable management. Concepts around non-point source contamination and geogenic contaminants are also treated in detail.