This text is intended for a senior/graduate level course in hydrosystems. Students who take this course must have previously taken a course in hydrology and hydraulics. The term "Hydraulics" can also be used to describe different types of water projects. The scope of this text covers both of these definitions. The major focus of the text is to bring together the use of mathematical modelling with the use of hydrosystems for the analysis, design, operation and managment of water projects. To accomplish this goal, the authors present the basic principles of optimization, probability, and risk analysis and then apply these principles to the areas of water supply management and water excess management. This text aims to go beyond the traditional uses of operations research techniques and statistics for river basin planning that are typically presented in the context of reservoir operation. The text has detailed coverage of microeconomics, linear and nonlinear programming, and risk and reliability analysis. These topics illustrate the use of optimization in hydrosystems. A solutions manual is available.