Recent advances in technology offer hydrologic engineers, watershed managers, and data collection agencies unprecedented capabilities for storing and manipulating data. With the advent of Digital Elevation Models (DEM), Triangulated Irregular Networks (TIN), Digital Line Graphs (DLG), and Geographic Information System (GIS) software, the use of watershed modeling among industry professionals has increased at an incredible rate. This growth in hydrologic application of models and modules has made it increasingly difficult for practitioners to choose the most effective use of the technology. This report serves as a guide to help professional select the most advantageous applications of GIS modules and distributed models for watershed runoff. It identifies state-of-the-art GIS hydrology analysis software and techniques, as well as, GIS types and map projections. In 7 chapters, it covers data commonly required for hydrologic analysis, limitations of available data, and the integration of watershed hydrological analysis software and GIS techniques. The appendix highlights 9 examples of watershed modeling systems including the Watershed Modeling System (WMS), the Soil and Water Assessment Tool (SWAT), and the Hydrologic Model CASC2D.