The study area of this research is the Qain Plain aquifer in South Khorasan Province, characterized by an arid and hot climate. In recent years, declining precipitation, limited water resources, uncontrolled drilling of agricultural wells, and excessive groundwater extraction have led to a severe drop in the groundwater level in this region. The objective of this study is to investigate groundwater resource modeling and apply quantitative models to simulate the aquifer flow of the Qain Plain, analyze water table fluctuations in piezometric wells, and propose management strategies to mitigate groundwater depletion.

This study utilized hydrogeological, hydrological, meteorological, and baseline groundwater resource data. For a detailed hydrogeological analysis, quantitative groundwater modeling was performed using the GMS software and MODFLOW code. The groundwater level was simulated over a three-year period (2020–2023) in 36 monthly time steps. The model was manually calibrated for the years 2020–2022 and validated for 2022–2023. After ensuring model accuracy, a crop pattern modification scenario for the Qain Plain was examined, and its impact on groundwater level recovery (while keeping other conditions constant) was analyzed in the plain’s piezometers.

The results indicate that implementing this scenario—shifting from high-water-demand crops to low-water-demand crops—would increase groundwater storage in the plain by 4969440 million cubic meters per year.