(364ap) System Dynamics Modeling for the 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, along 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 modelling (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 digital twin in the form of a stock and flow diagram, encompassing five intricately interconnected subsystems to assess the dynamics of water utilization, production, and the broader implications for energy supply and food production [3].

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. Three distinct scenarios—business-as-usual (BAU), climate change integration with energy transition (CCI), water integration schemes (WIS), and are examined over a 20-year modelling period. Notably, the WIS scenario emerges as the most promising, offering a significant increase in water availability compared to other scenarios, with a minimum of 20% improvement demonstrated. Moreover, when the nexus is optimized as a process using nonlinear programming the maximum water availability occurs in the 234^th month with water input more than double the BAU because of the increased influence of precipitation, river runoffs, and waste reuse.

These insights offer valuable guidance for policymakers and industry leaders in Cape Town and beyond, addressing similar water-related challenges. By leveraging these findings, stakeholders can better anticipate and manage potential crises, fostering sustainable water management strategies that are critical for the resilience and long-term success of urban areas. Building on this foundation, my work is now being adapted to address the unique challenges faced by communities in the United States, particularly those impacted by severe weather conditions in the Gulf of Mexico. I am eager to apply my expertise to support U.S. industry partners in developing innovative solutions for sustainable resource management and enhancing resilience against climate-related disruptions.

Keywords: WEF nexus; Climate change; Energy transition; Simulation; Optimization; System Dynamics Modeling

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.

[3] Egieya, J.M., Parker, Y., Hofmann, V.S., Daher, B., Gorgens, J., Goosen N.J. 2024. Predictive simulation of the water-energy-food nexus for the City of Cape Town. Science of the Total Environment. 934, 173289

Research Interests

• Multiscale energy systems design, integration, and process optimization
• Mathematical modelling
• Techno-economic and life-cycle analyses
• Supply chain design
• Water-energy-food nexus