Towards climate resilient municipal water supply in Bangkok: A collaborative risk informed analysis

Abstract

Typical top-down approaches to climate change adaptation in the water sector rely on climate models to inform the adaptation design. In view of the inherent uncertainty associated with these models, this study uses a combined top-down and bottom-up approach called Collaborative Risk Informed Decision Analysis (CRIDA). Using the case of the Metropolitan Waterworks Authority, Bangkok, this study demonstrates the application of the approach, which includes (a) identifying critical thresholds that impact the system’s performance, (b) unearthing the system vulnerabilities through a stress test (scenario analysis), and (c) identifying feasible adaptation interventions. Through a stakeholder consultation process, it was found that streamflow, salinity, and turbidity are the key performance metrics of the water supply system. A series of stress tests to the system was conducted by adjusting input variables assuming a wide range of possible future climatic conditions. Frequency curves of the various input variables were developed to facilitate stakeholders’ planning for impending risks and for improving the overall robustness of the water supply system. Based on the stress test results and past studies of the study area, the raw water source of the Metropolitan Waterworks Authority is expected to be more saline in the future with more frequent and severe low flow conditions, for which a number of adaptation actions were formulated and proposed. It is suggested to develop adaptation pathways that can address a range of expected impacts of future climatic conditions on the Bangkok water supply system. The methodology presented is useful for study areas where a model of the system is unavailable, and data limitation is a challenge.