The sustainable and equitable management of water requires integrated analysis which includes the integration of a multitude of modeling systems at the core. The linkage of the modeling systems and components is the main bottleneck to achieve the integrated modeling solutions that maintain the integrity of the entire environmental system for comprehensive analysis, planning and management. In this paper, the use of a Geographic Information System (GIS), as an integration framework for the water modeling systems, together with object-oriented data modeling and programming schemes is explained. Integration of the modeling systems on a GIS platform, through a surface-water-specific GIS data model, Arc Hydro, and interface data models as data repositories for common water features, hydrologic and hydraulic modeling elements, is presented with a case study. Arc Hydro served as an integration data model for the simulation models of concern. Time series data transfer between modeling system at the information exchange points is facilitated using object-oriented linkage programs, and relationships among the modeling elements are established through Arc Hydro.

In the case study, the HEC-HMS hydrologic model and the HEC-RAS hydraulic model are integrated into an automated floodplain mapping application on a GIS. The implementation of the integration methodology is presented.