Nowadays, with the rapid growth of population and increasing demands, water consumption in agriculture, drinking water, and industry has significantly increased. The shortage of surface water resources in many regions of the world has led communities to rely on groundwater pumping to meet their needs. Extensive and prolonged exploitation of groundwater resources can lead to numerous environmental problems, the most significant of which is land subsidence. In fact, the increase in effective stress within soil structures due to excessive groundwater extraction causes soil skeleton compaction, reduces porosity, and ultimately leads to land subsidence over time. Therefore, sustainable management of groundwater resources is critically important globally, especially in regions heavily dependent on groundwater. The Isfahan-Borkhar study area, one of the 21 study areas within the Gavkhuni basin, has experienced severe groundwater depletion and land subsidence due to population growth and the rapid development of industry and agriculture, despite its arid climate. Given the rapid increase in subsidence across the plain and its progression towards the city of Isfahan, implementing strategies to control this phenomenon is essential. This research focuses on modeling groundwater flow and land subsidence in the study area. To achieve this, a groundwater aquifer model for the period from August 2017 to the end of July 2021 was prepared using the MODFLOW code in the GMS graphical user interface. Subsequently, as post-processing of the groundwater model, land subsidence modeling was conducted using the SUB package. For calibration and validation of the groundwater model, monthly water level data from observation wells were used, and for calibration and validation of the subsidence model, results obtained from processing Sentinel-1 satellite time-series images were employed. The comparison of subsidence maps derived from satellite image processing with the hydrographs of observation wells indicated that areas of the aquifer experiencing the highest cumulative subsidence during the modeling period also showed significant groundwater level declines. Additionally, a strong correlation was observed between subsiding areas of the aquifer, the locations of extraction wells, and agricultural lands. Overall, the study revealed that subsidence in the study area is mainly due to groundwater depletion, but factors such as soil composition, grain size, and aquifer sediment thickness also contribute to the extent of subsidence. Finally, three scenarios were considered to eva‎luate the aquifer's response: extension of the current trend, a 10% reduction in groundwater extraction, and a 20% increase in groundwater extraction. Scenario eva‎luation showed that continuing the current trend would lead to further groundwater level decline and increased cumulative subsidence, especially in the southern part of the aquifer. The 10% extraction reduction scenario also reduced the groundwater level decline in the aquifer but could not completely stop the downward trend. The 20% extraction increase scenario caused severe groundwater level drops across extensive areas of the aquifer and expanded subsidence zones. To control groundwater depletion and land subsidence in the study area, stricter extraction limits, enhanced recharge in critical subsidence zones, and the creation of alternative water resources are necessary.

جهانگير عابدي كوپائي

سياوش ايرانپور , عاليه سعادت پور

محمد شايان نژاد , شمس اله ايوبي