Examining the evolving patterns of recent droughts and climate categorization's impact on groundwater reserves through the utilization of GRI and SPI indices in the southern plain of the Sefidroud Basin, Iran

Abstract Groundwater reservoirs are acknowledged as a vital and cost-effective water source, and comprehending their significance and efficient utilization can foster sustainable development of social and economic activities in a region, particularly in arid and semi-arid regions. This study aimed to explore the correlation between the GRI index and standard rainfall, followed by the classification of the region's climate using the De Martonne method. The research focused on analyzing the temporal variations in recent droughts and climate classification concerning underground water resources in the Qorveh-Dehgolan plain. The GRI calculation method was employed to assess groundwater depletion over periods ranging from 1 to 48 months in the Qorveh-Dehgolan plain. Additionally, ArcGIS software was utilized to zone the groundwater levels and drought severity. The study conducted a correlation analysis between GRI and SPI indicators through linear regression in Excel, revealing a lack of significant correlation between the two indicators (P-value = 0.053 and R² value = 0.003), despite their distinctiveness. Furthermore, the drought classification based on SPI indicated that the region fell into the normal drought category. The climatic classification derived from three nearby stations was established as semi-arid using the De Martonne method.