RESUMO
Decision-making associated with the promotion of water sustainability is subjected to uncertainties arising, on the one hand, from the current capacity of understanding socio-environmental systems and their temporality, complexity and multidimensionality; and, on the other hand, from the need to represent key aspects of these systems through data and information. Such a representation is often supported by indicators, indices and systems of indicators for relevant aspects of the problem and for a scenario under analysis. In this context, the main aim of this study was to develop a novel system of indicators for water sustainability assessment in river basins. Literature review and content analysis were used to define an analytical structure for the problem from the perspective of the natural, social and built capitals of related sustainable development assessment. Each capital has been hierarchically subdivided into categories, subcategories and attributes, leading to 54 aspects for water sustainability assessment. A list of indicators was compiled from the scientific and technical literature, linked to attributes, and associated with valuation ranges. This led to the proposition of the River Basin Water Sustainability Index (RBWSI) and sub-indices associated with categories and subcategories of the model. The timeframe and territorial scale relevant for assessment were defined as five-to-ten year periods and areas under the jurisdiction of river basin management committees, respectively. The new model and index thus proposed may be useful in water sustainability diagnostic and prognostic studies, such as required to assess the effectiveness of river basin management actions aimed at promoting sustainable development.