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Abstract

Iran is vulnerable to land subsidence hazards due to extensive groundwater pumping that poses a significant risk to its population and infrastructure. Measuring and monitoring groundwater decline and associated subsidence is crucial but challenging. Previous studies focused on specific areas close to big agricultural centers and metropolitan areas. This study aims to conduct a nationwide survey using Interferometric Synthetic Aperture Radar (InSAR) to provide a comprehensive picture of the problem. We conducted a small baseline subset analysis of Sentinel-1 data in the past seven years and isolated the subsidence by correcting other interferometric phase components, such as atmospheric delay. We calculate the time series of surface deformation at a spatial resolution of 100 m. Our results show that more than 70,000 sq. km of the country’s land is experiencing significant subsidence, primarily in agricultural areas. Assuming the subsidence is associated with pumping from confined aquifers, we estimate a yearly groundwater loss of 2.6 Billion Cubic Meters in Iran in agreement with independent in-situ measurements and GRACE data. Furthermore, we combine our estimated groundwater loss estimation with a land cover map and official agricultural production data and discuss how inefficient irrigation in certain parts of the country is responsible for most groundwater loss. Overall, the findings of this study suggest that urgent action is needed to address the problem of groundwater loss in Iran and mitigate its impact on the country's people and infrastructure.