Optimizing the Rainwater Harvesting and Roof Sprinkling System to Adapt to Urban Extreme Heat

Roof watering is a novel strategy for reducing air conditioning energy consumption and mitigating excess urban heat, yet its application is often constrained by water availability. To address this challenge, we propose an adaptation strategy that integrates rainwater harvesting tank with roof sprinkling to strengthen urban heat resilience. We develop a new module implemented in the Community Land Model Urban (CLMU) to evaluate the efficacy of the proposed strategy, whose parameters were further determined by a framework using multi-objective optimization combined with a transformer-based tabular foundation model. This integrated modeling framework enables the optimization of the proposed strategy and provides insights into its impacts on air conditioning energy consumption and its co-benefits on the urban thermal environment. Results show that the temperature threshold for triggering sprinkling is a more important parameter than rainwater tank size or sprinkling intensity. The optimal strategies effectively reduce cooling energy demand, lower extreme temperatures, and decrease heatwave days. However, a trade-off exists between rainwater tank size and the reduction in cooling energy consumption and heatwave days. Additionally, the energy saving is more pronounced under higher atmospheric temperatures. The implementation of the rainwater harvesting and roof sprinkling system in CLMU provides valuable insights for improving urban resilience and can be further coupled into Earth system model for large-scale studies.