عنوان مقاله [English]
Drought as a natural phenomenon, especially in arid and semi-arid climates such as Iran, is one of the most important challenges in the water supply. In this study, the hydrological drought has been investigated in the western sub-basins of Lake Urmia using the Surface Water Supply Index (SWSI) from Oct. 2009 to Sep. 2019. For this purpose, annual precipitation data, snow water equivalent, surface runoff, and reservoir storage (or changes in groundwater storage) have been used. The methodology of the study is based on the SWSI index, remote sensing using Google Earth Engine, determining the snow cover area using the NDSI index and analyzing the drought trend using the Mann–Kendall trend test. Also, according to the SWSI index, during the period of 10 water years, wet, extreme, and severe drought conditions not occurred in the study area, and generally, in 54% of cases near-normal conditions, in 19% of cases incipient drought conditions prevail and abundant , respectively. Also, from Oct. 2018 to Sep. 2019 was the wettest water year and from Oct. 2016 to Sep. 2017 and from Oct. 2011 to Sep. 2012 were the driest water years. In addition, in all studied sub basins except Zolachay, the near-normal hydrological condition was the most common condition during the study period. Also, the results of Mann-Kendall non-parametric trend test showed that only in the Baranduzchay and Rashkan-Talkhab sub basins, the trend of hydrological drought time series has been increasing (increasing humidity).