VI EWRA International Symposium - Water Engineering and Management in a Changing Environment Catania, June 29 - July 2, 2011 DECISION SUPPORT SYSTEMS FOR SUSTAINABLE DEVELOPMENT OF RIVER BASINS Eleni S. Bekri 1 & Panayotis C. Yannopoulos 2 (1) Department of Civil Engineering, Environmental Engineering Laboratory, University of Patras, Patras, Greece, e-mail: ebekri@upatras.gr (2) Department of Civil Engineering, Environmental Engineering Laboratory, University of Patras, Patras, Greece, e-mail: p.c.yannopoulos@upatras.gr ABSTRACT According to the European Water Framework Directive 2000/60/EC, all member states must formulate and implement Integrated River Basin Management (IRBM) strategies. Water resources management is not a straightforward task not only due to computational limits in modelling, but also due to the multiple interdependent processes (physical, biochemical, ecological, social, legal and political) that govern the behaviour of water resource systems. These processes are affected by uncertainties and by the unpredictable actions of multiple individuals and institutions involved in the management and operation of such systems. The Decision Support Systems (DSS) for River Basin Management (RBM) enable the comparison of water strategies for different scenarios based on the effects of multiple objectives. They can be used to support the planning and implementation of measures, as well as the communication between public authorities and other public or private stakeholders. The present paper aims to present the role and the importance of the DSSs in RBM, as well as the different decision making procedures for the sustainable management of river basins. The difficulties and the challenges in modelling technologies and in the development and implementation of such a tool for the Mediterranean watersheds are identified. Finally, a characteristic example of the most common stresses exerted in Mediterranean river basins and proposed goals/objectives for the development of a decision making procedure are included. Since the implementation of integrated and sustainable RBM is a big challenge, a model of a DSS that considers the special conditions observed in Mediterranean watersheds along with human judgment could be a precious informative tool for an effective decision-making of the administration bodies. 1 INTRODUCTION The importance of water for mankind and the dependence of life on it are beyond question. The key issue related to water is that there is often too much or too little, and the existent water amount is either too polluted or too expensive. Typical causes of this include degraded infrastructures, excessive withdrawals of river flows, pollution from industrial and agricultural activities, eutrophication from excessive nutrient loads, infestations of plants and animals, excessive fish harvesting, floodplain and habitat alteration from development activities and changes in water and sediment flow regimes. Moreover, the worldwide water availability and quantity are likely to further deteriorate