Abstract for: Assessing WEFE nexus policies under uncertainty in the Inkomati-Usuthu Water Management Area, South Africa, and the role of machine learning

The water-energy-food (WEF) nexus promotes holistic management of natural resources. The WEFE sectors are governed through governance systems and policies. Such policies are largely developed in silos. Better understanding of trade-offs for improved policy and governance design could lead to more effective resource management. This study assess nexus-wide policy impacts, using machine learning to search vast policy spaces and propose ‘optimal’ solutions for resources management challenges. Two approaches were used to build the WEFE system dynamics model: i) conceptual mapping and; ii) system dynamics modelling for quantitative assessment of trajectories. Outputs from the conceptual stage guided development of the SDM. Both approaches underwent multiple iterations and were validated by local partners in stakeholder workshops. A detailed report on the stakeholder engagement process can be found in NEXOGENESIS Deliverable 5.6 (Haupt et al. 2025; https://nexogenesis.eu/downloads/). Individual policy impacts tend to be confined to the sector to which they are developed. The land sector is a key impact driver. Food production drops up to 52%. Nitrogen leaching drops up to 37%. With all policies implemented, impacts across sectors are greater. Crop production increases up to 3x, nitrogen leaching drops up to 48%. GHG emissions are reduced up to 19%. Policy interactions are complex, with unanticipated impacts. A key result is that interactions between policies are not intuitive and may be counterproductive. Specific combinations were not tested due to hundreds of millions of combinations. A machine-learning tool, the NEPAT, searches this space and proposes ‘optimal’ policy combinations against different objectives. Trade-offs and compromise are the norm. The NEPAT highlights such trade-offs in a visually attractive environment. This study yields new insight for resources management in the IUWMA.