Water-Energy-Food-Ecosystems-Climate Nexus in the Water Reuse Sector. Current State, Gaps, and Challenges for Practical Applications

Under the current socio-economic situation, water security will get harder and harder to be assured, especially in the areas that would be more deeply affected by climate change such as the Mediterranean. It is paramount to diversify sources of water that cover the needs of agricultural, industrial, and domestic activities. Among other sources, water reuse is taken into consideration. But water reuse is tightly related to other sectors such as energy, food, and ecosystems, which are all also affected by climate. In this context, the water-energy-food-ecosystems-climate (WEFEC) Nexus concept emerges with the aim to provide comprehensive understanding of all those interlinked sectors, with the goal to develop and implement economic activities, political decision, and regulations that promote the efficient use of natural resources. The Nexus is a relatively new and evolving concept, which is highly related to plenty other emerging concepts such as sustainable development, circular economy, reuse and recycling, industrial symbiosis. Since 2017, the scientific community has witnessed a sudden surge in popularity for the WEFE Nexus (and its variations). However, despite its potential benefits, its practical application is still in its early stages, primarily limited to WEFC/WEFE Nexus R&D&I works. The great challenge is related to the implementation of standard assessment methodologies that could integrate all the elements and sectors involved in the Nexus in a way that they could properly represent local and global realities while expressing the results in an understanding way to approach them to wide audiences and relevant stakeholders. This chapter provides an overview of the role of the WEFEC Nexus in the water reuse topic. A review of current scientific articles and R&D&I projects was conducted to analyze the current state of the art. From this review, a list of methods and tools that have been used so far for preliminary Nexus assessment was collected. The review also enabled to detect current gaps that are also described in this chapter. Finally, based on the authors’ experience, some guidelines related to the future developments of the Nexus topic are provided.