This book traces the progress of hydrology and hydrogeology and highlights some of their key concepts and applications. Hydrology refers to the study of the movement, quality and distribution of the water on our planet as well as other celestial bodies. The three main sub-fields of hydrology are ground water hydrology also known as hydrogeology, surface water hydrology and marine hydrology. This text will provide significant information about these rapidly growing fields. It will give in-depth knowledge about the latest advances within this area and its uses in earth sciences. The book is an essential guide for both academicians and those who wish to pursue this discipline further. In this book, using case studies and examples, constant effort has been made to make the understanding of the different concepts of hydrology and hydrogeology as easy and informative as possible, for the readers.