This book attempts to provide information about the key concepts and theories related to the field of hydrology in comprehensive detail. It also discusses the modern principles and practices of this field. Hydrology refers to the study of all aspects related to water such as its movement, quality, distribution, type etc. Some of the prominent applications of hydrology are the estimation of rainfall, construction of dams, facilitation of potable water, development of urban drainage systems, among many others. This book is compiled in such a manner, that it will provide in-depth knowledge about the principles and practice of hydrology, enabling the reader to gain a thorough understanding of the subject. Students, researchers, experts and all associated with the discipline of hydrology will benefit alike from this book.