Abstract

Srepok is an important river basin in the Central Highlands region. In recent years, droughts have occurred more frequently, threatening the sustainable development of this region. Therefore, studying the characteristics and trends of droughts is extremely necessary to propose appropriate response solutions. In this study, data from 9 rainfall stations and 1 hydrological station during the period of 1982 - 2022 were used to assess the fluctuations of droughts over time scales. The Mann-Kendall non-parametric test method and Sen slope estimation were applied to analyze the trends. The results show that droughts start from August to November every year, about 2.5 times higher than the remaining months. The duration of droughts ranges from 5 to 15 months, with a median of 7 months. The SPI7 index recorded more severe droughts at a very severe level than SPI3 and SPI5, the most severe drought occurring in 1994. The SSI index also fluctuated strongly, especially in 2014 with SSI5 reaching 37.7. The strongest drought intensity was in 2004 and 2015 with SSI5 reaching 1.7. The SPI tended to increase in the dry season and decrease slightly in the rainy season. Although the period 1982 - 2002 had many droughts at a mild and severe level, the very severe drought tended to increase in the later period. The study shows that combining SPI and SSI to assess drought trends is effective, contributing to optimizing short-term and long-term drought response measures.