Drought Hazard Analysis Using SPI Index and GIS-Based Analytical Hierarchy Process in the Cai-Phan Rang River Basin, South-Central Coast of Vietnam

Drought is a naturally occurring event associated with a significant decrease in water availability over a region. Changes in hydrological conditions in the area, such as climatic changes, especially rainfall, can lead to droughts and floods, which have many negative impacts on life and nature. Adaptation to natural disasters, such as drought, can be effective through an improved understanding of disasters. Understanding their effects is of widespread concern and a great challenge to researchers and policymakers. Comprehensive hazard analysis will deepen the understanding of disasters. Many factors influence drought hazards, such as precipitation, temperature, flow and water balance, soil structure, and land cover. In the Cai-Phan Rang River basin, South Central Coast of Vietnam, the changes in water availability are significant concerns since they often lead to drought, forest fires, reduced agricultural productivity, poverty, and food insecurity. This study uses the Standardized precipitation index (SPI) to analyze the drought characteristics, including Probability, Intensity, and Duration; then apply the analytical hierarchy method (AHP), a multi-parameter modelling, to evaluate drought hazard in the Cai - Phan Rang River basin. The drought hazard zoning map was made based on the weight of the selected indicator using GIS (geographic information system). The results showed that drought has expanded and been prolonged in recent years, although the frequency is not significantly changed compared to the past. In general, low rainfall and high temperatures in the southeast regions of the Cai-Phan Rang River basin pose a high drought risk. Due to topographical characteristics, although located in the vicinity of low-elevation streams, the narrow delta area in the central valley of the basin is the area with the most elevated hazard. Besides, the local livelihood is closely dependent on agriculture and aquaculture, so this region should be prioritized in drought response strategies.