Multivariate and multi-temporal analysis of meteorological drought in the northeast of Thailand

Abstract

This study evaluates drought characteristics in the Mun River Basin, located in the northeast of Thailand. The basin is important from an agriculture perspective, as about 75% of the total area is under cultivation (a majority of which is without irrigation facilities). It is, however, also one of the most drought-prone regions in the country, and a proper understanding of drought characteristics can aid in planning and implementing drought mitigation and management strategies and measures in the basin. Using the Standardized Precipitation Evapotranspiration Index (SPEI), calculated from high-resolution climatic data during 1979–2017, we find that major drought events recur approximately every 6 years in the basin. A new approach to the use of thresholds to remove the effects of minor droughts is introduced. It is found to have improved drought characterization for prolonged drought events with low intensity. Drought events are evaluated for severity, duration, and frequency (SDF) using univariate and multivariate approaches at nine timescales (1-week to 24-months). Generalized Extreme Value (GEV) and Log-logistic (LL) are the most suitable distributions for SPEI calculation in the study area, though all three-parameter distributions have good fit at longer timescales. SPEI calculated at weekly timescales, especially during the vegetative stage of crop growth, show a good correlation with yields; thus, they can be useful for planning agricultural activities. Drought vulnerable assessment using joint occurrence probabilities of drought duration and severity indicates that most of the area in the western part and some area in the eastern part are the highest drought-prone regions in the basin. It is interesting to note that the drought prone areas of the basin are independent of the annual rainfall amount but are influenced by its temporal variability.