Potential risks of climate variability on rice cultivation regions in the Mekong Delta, Vietnam¹

Riscos potenciais da variabilidade climática nas regiões de cultivo de arroz no Delta do Mekong, Vietnã

HIGHLIGHTS:

Dry weather seasons overwhelmed the wet weather seasons across the Mekong Delta.

The 2014-2016 dry weather season was the driest, occurring in 75% of the Mekong Delta.

Coastal rice-producing regions are known by abundant water, but had significant downward trend in rainfall in recent years.

ABSTRACT

In recent decades, the rice cultivation regions in the Mekong Delta have continuously suffered from unprecedented weather events due to a decline in rainfall as part of climate variability. The aim of this study was to perform a comprehensive exploration of the rainfall characteristics across the area, applying the Rainfall Anomaly Index (RAI), Spearman Rho test and Sen slope estimator to help track the weather as well as provide warnings on the potential risks caused by alterations in rainfall amounts. For this goal, the rainfall data sequences at 14 national observation stations across the Mekong Delta were collected for the 1984 - 2019 period. Results indicated that the dry weather seasons occurred more frequently during the normally wet weather seasons. Four typical dry weather seasons were identified for the 1997 - 1998, 2002 - 2004, 2014 - 2016, and 2018 - 2019 periods. Among these, the 2014 - 2016 period was the driest, with 9 out of 12 stations in the area being extremely dry and RAI risk peaks as high as -4.86 at the Moc Hoa station in the province of Long An. A weather trend of decreasing rainfall was evident, mainly in the coastal sub-regions. The discovery of changing rainfall trends is valuable for predicting future climate variability.

Key words:
climate change; RAI; Spearman Rho tests; weather seasons