Readers of this book are not likely to learn the art of systems modelling and analyses unless they actually do it. The modelling approaches, examples and case studies contained in this book, together with the exercises offered at the end of most chapters, we believe and hope, will facilitate the process of becoming a skilled water resources systems modeler, analyst and planner. This has been our profession, indeed our hobby and source of enjoyment, and we can highly recommend it to others. Water resource systems planning and management is a multidisciplinary activity. The modelling and analysis of water resources systems involves inputs from the applicable natural and social sciences and from the people, the stakeholders, who will be impacted. It is a challenge.