This book is unusual in two respects: First, it is attributed to 5 authors, but in reality 15 authors have contributed different chapters. Second, each chapter is written by one or more authors. The book includes 25 chapters and 6 appendixes. For an authored book, this arrangement seems unusual. When different authors write different chapters, there is bound to be a certain degree of nonuniformity in style and breadth of coverage. This outcome is less likely when the entire book is written by the authors. Hydroinformatics is an area that is only a little over a decade old. During its short period of existence, it has witnessed phenomenal growth, fueled largely by unprecedented revolutions occurring in the information technology sector, as well as rapid advances in satellite technology, geographical information systems, data mining, database management systems, and data storage and retrieval systems. Applications of these technologies in civil, environmental, ecological, and water resources engineering have given birth to the newly emerging and rapidly expanding area called hydroinformatics. This healthy trend brings seemingly disparate areas closer. Hydroinformatics cuts across several disciplines—a point well emphasized in the book—and different disciplines now do not look so different after all. They indeed have a great deal in common—more than might appear at first sight. The book makes a real contribution in bridging different disciplines, and the authors are to be congratulated for preparing this book on hydroinformatics. The subject matter of the book is divided into six sections. After the book introduces data integrative studies in Chapter 1, the following five sections contain 24 chapters, and the remaining section contains six appendixes. The first chapter sets the stage for the material to follow, develops a rationale for the book, and goes on to describe its scope. The first section, comprising five chapters, deals with data-driven investigations and approaches in hydrology. The approaches described in these chapters have potential for application in other areas related to water and the environment. Chapter 2 deals with a unified modeling language UML . After introducing the basic aspects of UML, it discusses the framework of UML, structural software objects, UML relationships, UML diagrams, object model diagrams, and database designs and development. This introduction to the material is excellent. Chapter 3 deals with digital library technology for hydrology. This technology has applicability beyond the frontiers of hydrology. After