Assessment of drought hazard, exposure, vulnerability, and risk for rice cultivation in the Mun River Basin in Thailand

When assessing drought risk, most studies focus on hazard and vulnerability, paying less attention to exposure. Here, we propose a comprehensive drought risk assessment scheme combining hazard, exposure, and vulnerability. At the Mun River Basin, 90% of rice cultivation is rain-fed and regularly encounters droughts resulting in the lowest yields in the country. The water deficit calculated with respect to rice water requirement is used to assess drought hazard and is estimated at monthly time steps. We use drought severity and frequency for hazard estimation and population and rice field characteristics for exposure. Vulnerability is represented by physical and socioeconomic factors and coping and adaptive capacity. Between 1984 and 2016, monthly precipitation during the rice-growing season was insufficient to meet rice water needs at all growth stages (July-November). The hazard is more severe in October and November, which can lead to significantly reduced yields. People and rice fields in the center part of the basin are more exposed to drought than in other parts. Extensive areas are under high and moderate vulnerability due to low coping capacity. The higher drought risks appear in the last 2 months of the growing season and decrease from north to south, while the risk map of total precipitation demonstrates that most of the areas have low and very low risk. This emphasizes the importance of monthly time series analysis to calculate agricultural drought hazard and risk. Consequently, we recommend using the hazard and risk maps for October and November instead of the total precipitation to develop solutions to improve rice yield.