Spatial mismatch between recorded groundwater pumping and land subsidence in the alluvial plains of Alborz province, Iran: evidence from SBAS InSAR and multitemporal LULC analysis (۲۰۱۰–۲۰۲۴)

Groundwater-related land subsidence is widespread in Iran’s alluvial aquifers, yet the spatial correspondence between groundwater use, land-use/land-cover (LULC) patterns, and surface deformation remains poorly constrained. This study integrated annual Sentinel-۱ SBAS-InSAR line-of-sight (LOS) deformation for ۲۰۱۵–۲۰۲۴, Random Forest LULC maps for ۲۰۱۰, ۲۰۱۵, ۲۰۲۰, and ۲۰۲۴, a provincial pumping-well inventory, and temporally resolved groundwater-monitoring records across the Tehran–Karaj, Hashtgerd, and Eshtehard plains of Alborz Province. Direct LULC–deformation comparisons were restricted to exact same-year pairs for ۲۰۱۵, ۲۰۲۰, and ۲۰۲۴, and spatial dependence was addressed using variograms, distance thinning, and ۱۴-km block-level inference. Agricultural land declined by ۹۸.۹۹ km² (۱۴.۸۰%) between ۲۰۱۰ and ۲۰۲۴. Within the valid long-term InSAR footprint, ۶۳۶.۱۴ km² (۱۹.۲۴%) met the operational active-subsidence criterion of ≤ −۲۰ mm yr⁻¹. Agricultural land had the most-negative mean and median annual LOS deformation in all three matched years, with Kruskal–Wallis ε² values of ۰.۳۷۸, ۰.۲۲۲, and ۰.۲۷۳. This ranking persisted in ۴۲ of ۴۵ spatial-thinning configurations, while the agriculture–bare-land contrast remained supported at the ۱۴-km block scale in all three years. Static well data showed a further spatial mismatch: Tehran–Karaj contained the largest recorded pumping capacity, whereas Hashtgerd exhibited substantially more-negative long-term deformation. The recorded-discharge and subsidence-intensity centroids were separated by ۱۵.۱۶ km, and this distance varied only from ۱۵.۰۰ to ۱۵.۲۸ km across tested LOS thresholds. In contrast, a ۲۳-site temporal monitoring panel showed no robust contemporaneous or ۱–۲-year lagged association between monitored pumping intensity and annual LOS deformation. The results indicate that groundwater-use environments are persistently associated with stronger subsidence, but recorded pumping capacity alone does not explain its spatial distribution. Hydrogeological heterogeneity and groundwater-head history are therefore critical for interpreting and managing subsidence across the three plains.

کلیدواژه ها:

Land subsidence ، Groundwater pumping ، SBAS-InSAR ، Land-use/land-cover change ، Spatial mismatch ، Aquifer compaction ، Alborz Province ، Iran