Analysis of changes in time of drought on Groundwater resources of Garveh-Dehgolan plain using GRI and SPI

Groundwater aquifers are mainly recharged by precipitation or through interaction with surface waters, and the impact of climate change on precipitation and surface water will ultimately affect the groundwater system. The aim of this study is to use groundwater drought indices and standard precipitation to investigate the effect of drought changes on groundwater resources in the Qorveh-Dehgolan plain. For this purpose, the groundwater drought index was calculated and analyzed using groundwater information (piezometric wells) of the study area. The standard precipitation index was also calculated for different time scales using the CHIRPS database. Then, the relationship between the groundwater drought index and the standard precipitation index and annual precipitation was examined. The results showed that the groundwater drought index of the study area has a downward trend towards drought during the statistical period, such that the drought index has become negative since 2011 and the negative values ​​of the index continue until the end of the statistical period. Drought classification with standard precipitation showed that this region is in the near-normal drought category. The results of the correlation between the two indices using linear regression showed that there is no significant correlation between the indices (P-Value = 0.053 and R2 = 0.003), although they are affected by each other, and the low level of correlation between the indices can indicate the important issue that the groundwater drought situation in the Qorveh-Dehgolan plain is not only affected by meteorological drought in the region, and more important factors also affect the groundwater level of the plain, the effects of which on the groundwater level of the plain should be investigated.