Assessing the impacts of climate and socioeconomic changes on water availability and demand using the WEAP model: A case study of the Chi River Basin, Thailand

Chi River Basin, Thailand While climate impacts on hydrology are well studied, the combined influence of climate and socioeconomic development on water security remains poorly quantified for many monsoon basins. This study addresses this gap by integrating CMIP6 climate projections with localized urbanization, industrialization, and land use scenarios within the WEAP framework to project future water demand and unmet demand in the Chi River Basin (2026–2100). The analysis reveals that socioeconomic development pathways are a primary driver of future water stress, often exceeding the influence of climate uncertainty. Rapid industrialization and urban growth fundamentally shift the basin’s water-use structure, making industry a dominant demand sector by late century. Crucially, land-use policy—specifically the rate of agricultural land conversion, emerges as a powerful lever that can significantly reduce irrigation-related water scarcity even under high-emission futures. Water shortages remain acutely seasonal, with dry-period vulnerability heavily dependent on agricultural extent. These findings demonstrate that water security in transitioning agricultural basins is a socio-hydrological outcome, in which planning decisions on land use and economic development are as critical as climate adaptation. This integrated assessment provides a vital evidence base for aligning development policies with sustainable water allocation. • A WEAP-based framework evaluates climate and socioeconomic impacts on water demand and unmet demand. • Bias-corrected climate projections, together with observed streamflow, are applied to strengthen model reliability. • Water stress is assessed for agricultural, domestic, and industrial sectors under future scenarios. • Socioeconomic pathways are shown to intensify climate-driven increases in water demand and unmet demand. • Critical periods and sectors at risk of future water shortages are identified for regional water management.