Monitoring and analysis of hydrological drought based on the SWSI and satellite maps (case study: Khorramabad Basin, Lorestan, Iran)

Abstract

Drought, as a natural phenomenon, has turned water supply into a major problem in various regions of the world, especially in Iran, which has a dry and semi-dry climate. In this study, hydrological drought in the Khorramabad Basin was examined using the Surface Water Supply Index (SWSI) from 2011 to 2023. The study focused on analyzing drought trends in the study area using annual data of precipitation, snow equivalent water, surface runoff, and surface reservoir volumes (or changes in groundwater storage). The research methodology was based on the Surface Water Supply Index (SWSI), Google Earth Engine satellite imagery (GEE), Normalized Difference Snow Index (NDSI) for determining snow cover extent, and Mann–Kendall test for trend analysis of drought. The results obtained from the SWSI showed that during the 12-year studied period, very moist conditions and severe drought did not occur. Generally, hydrological drought was close to normal in about 80% of cases and had mild severity in 20% of cases. Additionally, 2020 was the wettest year, while 2018 was one of the driest hydrological years. Moreover, nonparametric Mann–Kendall test results indicated that changes in hydrological drought index did not follow a consistent trend throughout the basin.