Quantifying Vertical Land Motion and Underground Water Changes Using Space Geodetic Technique: Case Study in Kelantan, Malaysia

Abstract Geodetic methods are used to track the amount of vertical land displacement resulting from the extraction of surplus water from beneath. Excessive use of groundwater without recharge causes sediment deposition. It will bring a lower water level. When water has been pumped through the aquifer, the pore pressure can be reduced in the aquifer and will cause compaction of the aquifer. Excessive extraction of groundwater might result in land subsidence. The purpose of this study is to quantifying the vertical ground movement and underground changes in the area of Kota Bahru, and Tumpat in the state of Kelantan. The geodetic approach employed for quantifying land deformation involves the utilization of Persistent Scatterer InSAR (PS InSAR), while the monitoring of groundwater changes is accomplished by applying Gravity Recovery and Climate Experiment (GRACE). This analysis utilises 20 sentinel 1A scenes captured on the descending tracks between November 2015 and February 2021. In order to ascertain the rate of deformation in the research region, the GPS data obtained at the GETI station were compared. GRACE gravity data from 2003 to 2021 are used to calculate changes in terrestrial water storage (TWS) in the study region. GRACE offers temporal fluctuations in TWS, which includes soil moisture, surface water, and groundwater. According to the findings, the rate of land subsidence in Kota Bharu and Tumpat is around -0.6 mm/year, and -4.1 mm/year respectively. Results from GRACE shows that the equivalent water height at the study area is Kota Bharu -5.2336mm/yr and and Tumpat -4.0982 mm/yr. The findings indicate a correlation between changes in groundwater levels and vertical land movement as determined by various geodetic methods.