WaterWare is the outcome of Eureka EU 487, a collaborative research programme which had the objective of developing a comprehensive, easy-to-use decision-support system for river-basin planning. Its purpose is to assist government agencies, river-basin commissions, etc., in decision-making for the efficient management of water resources in terms of both quantity and quality. By combining the capabilities of geographical information systems, database technology, modelling techniques, optimisation procedures and expert systems, the aim is to improve the quality of decision-making in what is becoming an increasingly complex area. The first in this series of three papers outlines the aims and philosophy adopted in developing WaterWare. Thereafter, the system architecture, design features and facilities provided are described briefly.