Document Type : Original Article

Authors

Department of Geology, Faculty of Science, Ferdowsi University of Mashhad, Iran

Abstract

The development of agriculture and industry and the increase of population in countries with arid to semi-arid climates have led to more harvesting of groundwater resources and as a result land subsidence in different parts of the worlds. Decades of groundwater overexploitation in the Kashmar-Bardaskan plain in the north-east of Iran has resulted substantial land subsidence in this plain. The plain is considered as an arid to semi-arid zone and facing a negative water balance. The average annual precipitation in the plain is around 191 mm and the evaporation rate is 3956 mm. According to the unit hydrograph of the plain, the annual decline of water level is 1.12 m. In this study, the velocity of subsidence has been determined using Interferometric SAR technique (In-SAR) and radar images of Envisat ASAR and Sentinel-1 for a time period from 2003 to 2017. The results of an InSAR time series analysis indicated that an area of 1200 km2 with different speeds of 5 to 26 cm/year in the satellite line of sight (LOS) is subsiding. The results showed that in addition to the decline of groundwater level, subsurface conditions such as sediments types (fine-grained layers) and their thickness also affect the occurrence and amount of land subsidence.

Keywords