Water and environmental engineering is an area of engineering that aims to address environmental issues related to air, water and soil. It deals with the development and management of water resources; designing hydraulic structures such as dams and tunnels; water quality engineering; water resources engineering; outdoor and indoor air quality engineering; ocean engineering; and hazardous waste management. Entropy is referred to as a measure of the disorder or randomness of a system. It has been used to solve numerous issues in geographical, earth, and environmental sciences. In the field of water and environment engineering, it has numerous applications in areas such as water distribution networks, sediment transport, river flow forecasting, and water monitoring network design. This book aims to shed light on some of the unexplored aspects of entropy and its applications in water and environmental engineering. It will also provide interesting topics for research, which interested readers can take up. A number of latest studies have been included to keep the readers up-to-date with the global concepts in this area of study.