2Ecole des Mines de Paris

Alternative options for new private and public investment projects in the transboundary Mesta/Nestos River catchment between Bulgaria and Greece involve new dams and water storage reservoirs, agricultural irrigation systems, new touristic resorts and various water related facilities for urban and industrial water supply. These developments should be implemented in both parts of the basin (Greece and Bulgaria), where there are different socio-economic conditions and therefore different preferences and different objectives. Alternative options should consider environmental consequences, impacts to ecosystems and human health, and also financial and social risks. The impacts on the environment and their prevention should be weighted against the economic benefits and social consequences. Sustainable implementation of private or public utility projects cannot be achieved without public participation and a clear consensus between stakeholders. The UNESCO HELP initiative provides a rationale for breaking the “paradigm lock ” existing between the most recent scientific findings on the one side and the public, stakeholders and decision makers on the other. In this paper stakeholder involvement in the decision making process is promoted firstly by communicating the results of integrated modelling of water resources management at the basin scale, and secondly by suggesting alternative models and software in order to facilitate negotiations and final decisions in transboundary water resources management. These are based on ranking different projects according to (1) every country’s stakeholders ’ own objectives, (2) aggregating the stakeholders ’ different objectives for both countries and (3) aggregating the countries ’ different objectives. KEY WORDS