Quantifying groundwater exploitation induced subsidence in the Rafsanjan Plain, southeastern Iran, using InSAR time-series and in situ measurements

Abstract

Decades of groundwater overexploitation for agriculture and industrial development have resulted in substantial land subsidence in the Rafsanjan plain of southeastern Iran. This work presents the results of an InSAR time series analysis obtained by the exploitation of Envisat, ALOS and Sentinel-1 (S1) SAR data archives between June, 2004, and May, 2016, to investigate land subsidence in the plain. The InSAR analysis revealed an area of approximately 1000 km2 within the study area showing subsidence of greater than 5 cm/year and locally exceeding 20 cm/yr in the last decade. This area of significant subsidence is limited in its spatial extent to the agricultural land and is partly influenced by Quaternary faults. The temporal and areal relationships of subsidence and groundwater level data suggest that a significant part of the observed subsidence in the Rafsanjan region is caused by intense groundwater extraction that has led to widespread compaction within the upper parts of the up to 300 m thick unconsolidated sediments, causing irreversible and inelastic deformation of the aquifer. The average volume storage loss of the aquifer system due to overexploitation is estimated to have been approximately 300 million cubic metre (mcm)/yr over the last decade.