Exploring pathway scenarios for future urban water resilience using systems approach coupled with an agent-based...

This study develops a hybrid system dynamics model coupled with an agent-based model, operating on synthetic social-policy networks, to project future scenarios for water supply and demand dynamics in Singapore. The simulations explore multiple trajectories involving population growth, reductions in imported water, and varying local catchment levels, each evaluated under different policy coverage rates (the proportion of the population motivated by conservation policies). These scenarios are ranked at three future time points according to the volume of water required from alternative sources, namely desalination and recycled water. In the near term (2030), among the assumed trajectories, a rapid decline in imports sharply increases pressure on alternative water sources. By the mid (2045) and long term (2060), however, policy coverage begins to exert a more substantial influence: in approximately 55% to 60% of the best-performing scenarios, a 20% policy coverage rate is associated with reduced reliance on alternative sources. The simulations also reveal two emergent behaviors in response to policy interventions. First, policy coverage generates a cumulative, long-term effect: in 2030, the difference in per capita demand between scenarios with and without policy intervention is 3.4 lpcd (liters per capita per day), increasing to 20.3 lpcd in 2060 in one scenario. This highlights the importance of early and sustained policy engagement to achieve long-term savings. Second, per capita demand reduction plateaus beyond a 30% policy coverage rate, owing to a lower-bound cap imposed on low-consumption agents to maintain equity. Overall, the hybrid model provides policymakers with informative feedback through a range of what-if scenarios, supporting more robust long-term planning and preparedness.