Identifying and prioritising adaptation options for a coastal freshwater supply and demand system under climatic and non-climatic changes

Coastal freshwater supply and demand systems are expected to be significantly affected by changes to both climatic and non-climatic drivers over coming decades. Adapting to these changes to secure adequate freshwater to meet the rising demands of socio-economic development has become a critical task for decision-makers. Whilst a range of adaptation options may be available, the complexity and interconnectedness of water resource systems make it challenging to identify which options are likely to be most feasible and effective. Here, we present a Bayesian decision network (BDN) that was co-developed with local experts to identify appropriate adaptation options for freshwater management under both current and likely future conditions in the Da Do Basin of coastal Vietnam. Potential adaptation options were prioritised according to cost-effectiveness based on relative costs incurred and relative utilities delivered across a range of future scenarios. The BDN model indicated that cost-effectiveness of adaptation options varied between future scenarios. Constructing pumping stations was the most cost-effective option under climate change scenarios, whilst a higher water price was the most cost-effective option under non-climatic changes. Under combined climatic and non-climatic changes, constructing pumping stations in combination with increasing water prices provided the most cost-effective option. The model affords an opportunity for decision-makers in the Da Do Basin to prioritise and evaluate appropriate and feasible adaptation actions under different scenarios with respect to multiple drivers.