Assessing the microclimatic cooling potential of heritage water bodies in a hot-arid desert climate of Jodhpur, India using ENVI-met simulations

Urban warming is challenging the resilience of urban systems with extreme heat events, especially in developing countries with significant low-income neighborhoods. Nature-based solutions (blue and green infrastructure) are effective low-cost sustainable solutions for heat adaptation and mitigation. We discuss the microclimatic cooling potential of heritage blue infrastructure (waterbodies) in hot-arid city of Jodhpur, India, a significant tourist destination in the Thar desert region. Jodhpur witnesses extreme arid heat for almost 8 months annually with summertime Air Temperature (T_a), frequently reaching 48^OC. The old quarter (blue city) of Jodhpur exhibits income disparity and has distinct urban morphology and numerous heritage waterbodies (stepwells and tanks). We employed a 3D CFD model ENVI-met to simulate one stepwell and one water tank to assess their cooling efficacies for various conditions in summer and winter at a finer 1mx1mx1m spatial resolution, compared to existing ENVI-met studies mostly operating at 2mX2mX2m or 3mX3mX3m resolutions and validated the models with field data. These waterbodies exhibit complex geometry and are surrounded by high-density urban morphology dominated by sandstone structures with the presence of low vegetation. This is a first-of-its-kind study attempting to model complex geometry water bodies at a fine resolution in a similar high-density context. Our validation results show that ENVI-met can simulate such conditions as with a high index of agreement between simulated value and field observations. We analyzed Air Temperature (T_a), Relative Humidity (RH), Mean Radiant Temperature (T_mrt), and Physiologically Equivalent Temperature (PET) to evaluate outdoor thermal comfort and conclude that heritage waterbodies are capable of providing ambient comfort in an arid context. Results obtained can help provide insights on: 1) fine-scale ENVI-met simulations for modeling blue infrastructure and complex geometries, 2) role of humidity in providing ambient comfort in arid conditions, and 3) heat mitigation strategies for tourists and locals in heritage sites.