Decision-making processes in water resources projects are often multi-criteria and multi-objective, meaning there are numerous factors that influence decisions and there are often several objectives that are sought. (An example would be balancing a precious water supply between agriculture use and drinking water.) The main concern in utilizing multi-criteria and multi-objectives decision-making techniques is that different techniques may result in different outputs; therefore, selecting an appropriate technique is crucial. This book will describe fundamental concepts, technical and economic aspects, and practical real-world applications for different decision-making techniques.