A Shared Vision on the Transboundary Water Management Challenges of the Tagus River Basin

The Tagus River basin faces a growing water management challenge, as water demand and river regulation by large multi-purpose reservoirs lead to situations of water scarcity and mediocre conditions in some water bodies. The current situation and the impacts of increasing water demands are evaluated by a detailed river basin model which covers the whole river basin and includes the main hydraulic infrastructures and water uses of Spain and Portugal. Several indicators are computed from the model results to assess water demand satisfaction and the alteration of the hydrological regime, offering a better understanding of current hydro-climatic conditions in the basin. Results show that current water management practices have significantly altered the natural river flow conditions in the entire Tagus River basin. Water managers struggle to satisfy existing waters uses and increasing water demands will further accentuate these problems. The enforcement of new and planned environmental flow requirements may alleviate the conditions of some water bodies but will decrease the level of satisfaction of non-priority water demands. As additional measures are needed to improve water bodies status, water management and allocation policies must be revised at the river basin scale to improve the balance between water consumptive uses and environmental needs. A shared knowledge base and a common vision on the basin challenges will be required to achieve these goals and the datasets and tools applied in this study contribute to this needed transboundary cooperation.