Variable Hydrology may have significando effects on the availability of water resources at a basen scale. This work Analyzer impacts of variable Hydrology on the management of the lower course of the Ebro River that supplies water to the region of Catalonia, Spain. To perform the analysis, a river system modelo is developed using the modeling platform, RiverWare. Several hydrologic scenarios will be evaluated to project future water availability and the basen s ability to meet its demanda. Finally, this study will illustrate the usefulness of using modeling tools, such as RiverWare, for river basen planning and management.