Deciphering the relationship between meteorological and hydrological drought in Ben Tre province, Vietnam

Abstract

Abstract The low-lying Vietnamese Mekong Delta (VMD) is a key agricultural production landscape increasingly threatened by anthropogenic stresses and climate change. Droughts due to extreme events, climate change and upstream developments affect the delta. This paper explores the relationship between the intensity, duration, and frequency of meteorological droughts and hydrological droughts using a range of indices. We used monthly rainfall and stream flow data for the period 1992–2021 to calculate the stream flow Drought Index (SDI), the Standardized Precipitation Index (SPI), and the Reconnaissance Drought Index (RDI) for different time intervals. We found no observed time lag, and a strong correlation coefficient between upstream hydrological and downstream meteorological drought events assessed over long-term scales (i.e.,12-months). This is true for all downstream sites, except Ben Tre City. Meteorological drought events onset lagged 5–6 months, 6-month, and 4-month behind hydrological droughts at mid- and shorter assessment time scales (9-,6-, 3- month). Average correlation coefficient between hydrological indices and SPI and 9–3 month time scales ranged only from moderate to weak. These findings shed light and advance the understanding of the progression of meteorological to hydrological droughts in the VMD. Our results aid the regional understanding of drought onset and the causative mechanism at work, important for both medium and long-term drought forecasting and adaptation planning.