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An application of InSAR technique to monitor the subsidence induced by the excess groundwater withdrawal

Mani Hosseini(1,2,1), Mohamad.javad Valadan(3), Mohamad Reza Mobasheri(4) and Maryam Dehghani(5)

(1) K.N.Toosi University of Technology, , K.N.Toosi University of Technology, No. 1346,, 0098, Iran
(2) K.N.Toosi University of Technology, Geodesy and Geomatics Engineering Faculty, K.N.To, 0098, Iran
(3) , K.N.Toosi University of Technology, Geodesy and Geomatics Engineering Faculty, K.N.To, 0098, Iran
(4) Geodesy and Geomatics Engineering Faculty,, , No. 1346,, 0098, Iran
(5) Geodesy and Geomatics Engineering Faculty, K.N.Too, , No. 1346,, 0098, Iran

Abstract

A significant land subsidence has been detected in the northeast of Iran, located in the vicinity of the city of Mashhad. Excess groundwater withdrawal and rainfall decrease have resulted in a substantial drop in water table and subsidence occurrence in Mashhad basin. Interferometric SAR (InSAR) capability has been proven in the detection of land subsidence. Moreover, this technique is widely used to map the extent of the deformation area. In this study, InSAR and GPS techniques were applied in order to identify the seasonal surface deformation in Mashhad basin. InSAR time series analysis was utilized in order to estimate the subsidence rate using ENVISAT C-band data spanning between 2003 and 2006. The maximum deformation rate estimated by InSAR technique is 15 to 20 (cm/yr) while the continuous GPS measurements collected at Toos station from 2005 to 2006 determined the subsidence rate as 20 (cm/yr). Since the mean displacement velocity map obtained from InSAR highlighted the major and minor surface deformation features, it allowed us to design an optimum GPS network. Therefore, it was possible to evaluate the InSAR time series results. Furthermore, the horizontal components of the deformation were determined through the new GPS network. In order to relate the surface deformation to the amount of water withdrawal, the ground water level fluctuations were compared to the InSAR results. The comparison showed that the subsidence rate is associated with the descending trend of ground water level. This relationship is not necessarily linear at every point.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry