Mapping water provisioning services to support the ecosystem–water–food–energy nexus in the Danube river basin

Water, food and energy are at the core of human needs and there is a boundless complex cycle among these three basic human needs. Ecosystems are in the centre of this nexus, since they contribute to the provision of each component, making it imperative to understand the role of ecosystems in securing food, water and energy for human well-being. In this study we aimed to map and assess water provisioning services and associated benefits to support the ecosystem-water-food-energy nexus by taking into account environmental flow requirements for riverine ecosystems using the hydrological model SWAT (Soil and Water Assessment Tool). We developed a framework which includes indicators of water supply (capacity of ecosystem to provide water) and water use (service flow) and we applied it in the Danube river basin over the period 1995-2004. Water scarcity indicators were used to map the possible environmental water scarcity in the subbasins, and analyse the spatial match of water supply and water use. The results show that modelling is instrumental to perform the integrated analysis of the ecosystem water-food-energy nexus and spatial mapping is a powerful tool to display the environmental availability of water provisioning and regulatory services delivered by ecosystems and can support the nexus analysis