Multiscale Drought Assessment in Kien Giang Province, Vietnam: Comparing MSPI and MSPEI for Monitoring in a Coastal Mekong Delta Setting

Drought is a recurrent hazard in the Vietnamese Mekong Delta (VMD), with major implications
for agriculture, water resources, and rural livelihoods. This study assesses drought
variability in Kien Giang Province, Vietnam, from 1992 to 2024 using two multiscale
indicators: the Multivariate Standardized Precipitation Index (MSPI) and the Multivariate
Standardized Precipitation Evapotranspiration Index (MSPEI). Principal Component
Analysis (PCA) was applied to Standardized Precipitation Index (SPI)- and Precipitation
Evapotranspiration Index (SPEI)-based time series spanning multiple accumulation periods
(3–48 months) to derive integrated drought signals and to reduce redundancy across
timescales. The results show that the first principal component (PC1) captured a high proportion
of total variance across stations, indicating strong coherence in drought dynamics
across the province. Both MSPI and MSPEI successfully identified major historical drought
episodes, particularly the severe events of 2004–2005 and 2015–2016. However, the two
indices differed in their temporal behaviour: MSPI responded more directly to precipitation
deficits, whereas MSPEI showed slower post-drought recovery in recent years, suggesting
greater sensitivity to evaporative demand and climatic water-balance stress. These differences
indicate that evapotranspiration-sensitive indices may provide added analytical
value in warming coastal environments. Overall, the combined multiscale framework
offers a robust basis for drought monitoring, comparative assessment, and water-resource
planning in Kien Giang and other drought-prone coastal delta settings.