Written for hydrologists, GIS specialists, and scientists from many disciplines who create computer models of water resources, this book presents an improved standard for creating and using data in hydrologic projects. The ArcGIS hydro data model is the latest innovation in GIS modeling and increases the potential to integrate data from many sources to solve a wider range of water resource problems. This guide shows how hydrology projects work and how they can work better: by integrating local, regional, national, and international data to create a deeper understanding of the earth's water problems.