Water is an essential natural resource for life. Nowadays, water contamination is a common issue due to a variety of sources but mainly of anthropogenic origin, such as urban and industrial wastes. Methods for evaluating water availability and reliability in supplying needs for agricultural, municipal, and industrial water use, environmental flows, electric energy generation, and reservoir storage are described in this book. This book also discusses chemical threats in drinking water; removal of radioactivity from drinking water; and irrigation agriculture.