Assessing the Impact of Climate Change on Water Resilience: A Case Study of Rooftop Rainwater Harvesting in the West Bank, Palestine

Access to safe and reliable water resources is one of the most critical global challenges of the twenty-first century. In developing regions, such as Palestine, ensuring adequate water access has become increasingly difficult due to rapid population growth and the intensifying impacts of climate change, which place additional pressure on limited water resources. In this context, alternative water sources, such as rooftop rainwater harvesting (RWH), represent a promising option for enhancing water resilience. This study assesses the impacts of climate change on water resilience in the West Bank by evaluating the future performance of rooftop RWH systems. The potential effects of climate change on optimal storage capacity, system reliability, and deficit ratio are assessed spatially across different West Bank governorates. Monthly rainfall projections for the period 2021–2100 were obtained under three climate change scenarios (SSP126, SSP370, and SSP585). The results indicate that climate change is expected to negatively affect both optimal storage capacity and system reliability, with the most pronounced impacts occurring under the high-emission scenarios. However, the magnitude of these impacts varies spatially among governorates. At the West Bank level, the reliability of the RWH system decreases from 38% to 34% when shifting from the low-emission scenario to the high-emission scenario. Additionally, the optimal storage capacity and the harvested volume will decrease from 65 m3 to 58 m3. This study is the first in this area to use the mass balance approach to predict the future impact of climate risk on the storage capacity of rooftop rainwater harvesting systems. Overall, the findings provide a comprehensive assessment of the feasibility of rooftop RWH as a mitigation and adaptation measure to climate risks and its potential role in enhancing water resilience in the West Bank. This study presents the full framework for assessing the reliability of rainwater harvesting systems under conditions of climate uncertainty.