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Drought is known as the most hazardous natural phenomenon. Although the phenomenon is not preventable, its destructive effects can be reduced by taking some measures. Groundwater is severely affected by drought but has less considered. This study aimed to investigate the impact of meteorological drought on groundwater in the Kashkan Basin. Karkheh Basin is divided into three sub-basins: Karkheh, Kashkan, and Seymareh, of which Kashkan Basin is one of them. Also, Karkheh Basin is divided into 35 study areas, of which six study areas named Pol Dokhtar, Kuhdasht, Khorramabad, Shiravand, Aleshtar, and Chaghalvandi are located in Kashkan Basin. Groundwater Resource Index (GRI) and Standardized Precipitation Index (SPI) indices were used in this research. Then, the SPI index at monthly, quarterly, and annual time scales and the GRI index during the statistical period of 1985-2021 were used to investigate the drought condition and its impact on groundwater resources in the Kashkan basin. In addition to the seasonal and annual scales, the mentioned indices were also calculated on 3, 6, 9, 12, 18, 24, and 48-months. In the next step, the level of groundwater vulnerability in monthly, seasonal, and annual time scales was assessed using the above indicators. The most extended drought period and frequency were obtained using the total Drought Magnitudes (DM) criterion. Moisture status for each period was determined with the values obtained from SPI and GRI indices, and thus the trend of meteorological drought and groundwater in the basin was investigated. The correlation between different time scales of the SPI index (with and without the time delay), with average groundwater level and the GRI, was evaluated. The analysis results in this study showed that with increasing time scale, the correlation coefficient of SPI rises with the average groundwater level and GRI index. Also, meteorological droughts rate with time delay affects groundwater resources. The coefficient of determination (R2) showed that less than 40% of the variance of the groundwater level was affected by meteorological droughts, and more than 60% of it was affected by other factors, especially water pumping for agriculture and other water-consuming sectors.
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