The new ethic of sustainable development reinforces and extends the main principles of water resources management. Computer-based decision support systems are explored in order to identify their role in the implementation of these principles into water resource management practice. The presentation is divided in two parts. This article starts with the general definition of sustainable development. A set of principles is then identified, and a short discussion of three main subsystems (ecological, economic, and social) follows. The main discussion is devoted to decision support systems (DSS) and their role in sustainable development. Discussion of DSS characteristics, architecture, and main components is provided, with special emphasis on the modtjications required to address the principles of sustainability A second article in this issue presents four successful case studies of decision support systems for sustainable management of water resources.