Socio-hydrology and water-energy-food-ecosystems (WEFE) Nexus approaches to explore water scarcity in an alpine catchment in Northern Italy

The Alps play a vital role in regulating water supply for densely populated and agriculturally intensive downstream regions. Yet climate change is raising concerns over the development of water scarcity in mountain areas historically perceived as water abundant. Addressing these challenges requires understanding interdependencies across water uses, i.e., the Water–Energy–Food–Ecosystems (WEFE) Nexus, and untangling the coupled social and hydrological processes that contribute to creating water scarcity. We present a novel methodological framework that integrates Causal Loop Diagrams and the Network of Action Situations to jointly map socio-hydrological dynamics and the multi-level decision-making processes through which rules, institutions and practices influence water use, allocation and management. We apply this framework to the Orco catchment (Northern Italy), which has experienced recurrent summer droughts and water scarcity over the past two decades. Results show that trade-offs across the Nexus arise not only from hydroclimatic variability, but also from socio-economic factors creating levers and barriers to change, and an underlying condition of overallocation of water resources. At the same time, evidence of cross-sectoral synergies is found in both formal instruments (e.g., hydropower concessions and sectoral policies) and through informal, drought-triggered coordination among water users. Two venues of decision-making are central to addressing water scarcity: (i) the governance of hydropower reservoir, which is shifting towards a multipurpose use, and (ii) the implementation of environmental flow requirements, where weak knowledge links between socio-hydrological processes and decision-making create divergences among local actors but also  opportunities for collaboration across sectors. By integrating CLD and NAS, our approach maps the cause–effect chains that generate trade-offs among sectoral goals, deepening the understanding of the root causes of water scarcity and providing a basis for more coordinated and resilient governance of water resources in mountain regions.