Ethical issues and legal principles regarding joint management of shared river basins in the context of climate change and water scarcity in the Iberian Peninsula

Portugal and Spain share five large river basins. The human activities carried out in the rivers or in the river basin area generate mutual interferences and impacts on the quality and quantity of water and on the ecologic conditions of the rivers and surrounding ecosystems. Furthermore, the effects of climate change on river ecosystems in the Mediterranean region—namely drought, water scarcity, desertification, flooding, heat waves, soil salinization, invasive species—are leading to larger water stress periods and an overall reduction of ecosystem services. In this context, the main ethic challenges regarding joint management of shared river basins in the Iberian Peninsula are: territorial equity, geomorphologic equity, demographic equity, interspecies equity, development equity, intergenerational equity and cultural equity. To address these challenges, a set of principles of international environmental law are briefly analysed. These principles govern the relations between States, regulate the access to the rivers, preserve the ecologic equilibrium of the rivers, and influence risk management. The principles also limit State discretionarily towards possible river uses and shape international agreements to be adopted in the future.