“Nexus” analysis using Participatory System Dynamics Modelling and agro-hydrological Modelling: hints from an agricultural basin in Central Italy

The “Nexus” concept has emerged as an effective approach to natural resources management, that integrates management and governance across sectors and scales, emphasizing the need to consider interconnections and interdependencies among multiple sectors and dimensions. Research over the past decade has contributed to developing tools and methods for effectively mapping and analyzing these interdependencies, and the use of mixed qualitative/quantitative modeling of the Nexus is seen as a relevant opportunity. Stakeholder engagement in Nexus modeling remains crucial to ensure that policy-relevant messages are produced. Focusing on the Tarquinia plain (Italy), where a strong interdependency (and conflict) exists between agriculture and the state of the environment, this study applies both a participatory Causal Loop Diagram (CLD) and a agro-hydrological model (SWAT) to analyze a Nexus system. The combination of these tools is mainly functional: the CLD facilitates participatory Nexus mapping and helps stakeholders identify key challenges, while SWAT provides an in-depth analysis of those challenges, quantifying the impacts of drivers (e.g., climate change) and the potential effectiveness of measures. Attention is given to soil loss assessment and erosion rates, as an effect of irrigated agriculture. The study highlights the potential of the proposed approach to support finding suitable strategies to guarantee a balanced and sustainable development of areas where a strong Nexus among societal and environmental needs exists.