Land surface deformation monitoring in the Al-Ain arid region (UAE) using microgravity and SAR interferometry surveys.

The integration of geophysical and satellite-based monitoring techniques can yield new insights in land surface deformation (LSD) studies. In this study, we integrated the microgravity monitoring geophysical technique with Interferometry Synthetic Aperture Radar (InSAR) to reveal the possible sources of LSD changes. A microgravity survey was conducted over Al-Ain city for 1 year at one-month intervals, with time-lapse microgravity changes calculated based on the results. Over the same area of interest and time interval, InSAR analysis was performed using Sentinel-1 (C-band) data. The time-lapse microgravity changes for the whole studied period ranged from -36 to 365 μGal. The InSAR processing showed periodic land surface deformation over the area of interest varying with the season of the year. The InSAR technique detected land surface subsidence at the northeast and western parts of the study area (-7 mm/year and -8 mm/year, respectively) and land surface uplift in the central and southern parts of the study area (2 mm/year). The recorded subsidence may relate to water extraction in these areas. The integration of the two techniques showed a negative correlation, with coefficients of -0.43 and -0.39 for land surface subsidence and uplift, respectively. Furthermore, groundwater level drawdown zones were identified in the west and center of the study area. Overall, LSD is mainly stimulated by water volume exploitation in the Al-Ain region.