Abstract: This paper examines how various combinations of geographic information systems and simulation models have been used to advance knowledge of water resource assessment and management. The contribution of geographic information systems to the generation, management, and delivery of spatially distributed data, the advent of new geographic information systems tools, and the role of systems in hydrologic models and water resource decision support systems are reviewed. This review identifies some important research needs in addition to recent accomplishments, and these needs are used to identify the University Consortium for Geographic Information Science research and education challenges and/or areas within these challenges that are particularly relevant to the water resource domain. Four sets of innovations required for improved water resource management are noted, and areas of priority for research and education if geographic information science is to help solve water resource problems in the future are identified.