(128e) System Dynamics Modeling for Sustainable Urban Development in the City of Cape Town: A Water-Energy-Food Nexus Approach

Between 2015 and 2018, the City of Cape Town (CoCT), South Africa, confronted an unprecedented water scarcity crisis known as Day Zero, marked by the near-complete depletion of its municipal water supply [1]. This critical situation was precipitated by a significant decline in rainfall, leading to one of the severest droughts on record, and was further exacerbated by rapid population growth and urbanization. These factors, coupled with increased urban energy consumption and food demand, posed a significant threat to the city's water resources.

In response to this complex crisis, this study adopted a system dynamics modeling (SDM) approach [2] to explore the intricate interdependencies among water, energy, and food (WEF nexus). Utilizing Stella Architect, a comprehensive model was constructed as a stock and flow diagram, encompassing five interconnected subsystems to assess the dynamics of water utilization, production, and the broader implications for energy supply and food production.

The study aims to explore the long-term impacts of interconnected variables on Cape Town's water security, with a particular emphasis on understanding the influence of environmental changes and urban development patterns. Four distinct scenarios—business-as-usual (BAU), climate change integration with energy transition (CCI), water integration schemes (WIS), and food habit change (FHC)—are examined over a 20-year modeling period. Notably, the water integration scheme emerges as the most promising, offering a significant increase in water availability compared to other scenarios, with a minimum of 20% improvement demonstrated.

These insights are poised to offer valuable guidance for policymakers and urban planners in CoCT and beyond, grappling with similar water-related challenges. By leveraging these findings, stakeholders can better anticipate and address potential crises, fostering sustainable urban water management strategies that are crucial for the resilience and prosperity of cities worldwide.

References

[1] Hachaichi M., Egieya J.M. 2023. Water-food-energy nexus in global cities: addressing complex urban interdependencies. Water Resources Management. 4, 1911-1825,

[2] Wen, C., Dong, W., Zhang, Q., He, N., Li, T. 2022. A system dynamics model to simulate the water-energy-food nexus of resource-based regions: A case study in Daqing City, China. Science of the Total Environment. 806, 150497.