Assessment of long‑term rainfall trends and variability in the Vietnamese Mekong Delta: implications for water resources management strategies

The water budget in the Vietnamese Mekong Delta (VMD) depends heavily on rainfall which play crucial roles in supporting agriculture, aquaculture, and local livelihoods. This study evaluated rainfall trends across the VMD from 1978 to 2022, revealing significant spatial and seasonal variations. While a few inland stations showed marginal increases in dry season rainfall, our findings indicate an overall decline in both wet and dry season rainfall across the region. This trend is particularly concerning for coastal areas, such as Ca Mau Province, which rely predominantly on rainfall due to limited upstream inflows; these areas recorded substantial declines in annual and wet season rainfall, with Sen’s slope values of –7.582 mm/year and –6.335 mm/year, respectively. Although the VMD is situated within the Asian monsoon region, geographical factors, including coastal and inland locations, exert a strong influence on rainfall variability patterns across the delta. The observed rainfall decline has critical implications for water resource management in the VMD, where climate variability is projected to increase. Although other factors, such as evapotranspiration and land use changes, also impact water availability, our study focuses on rainfall’s direct role. These findings highlight the necessity for adaptive water management strategies that account for declining rainfall, particularly in vulnerable coastal areas. This study provides a critical analysis of rainfall trends in the VMD to inform adaptive water resource strategies under climate variability, answering how these long-term trends affect the region’s water availability and resilience, and contributes to the broader understanding of climate change impacts, informing both regional adaptation strategies and global climate policy formulation.