Sentinel-1 data monitoring Land Subsidence and Groundwater dynamics in the populous cities of Rajasthan, India

In India, around 80% of the population uses groundwater (GW) for their basic needs, out of which more than 60% are for agricultural activities and 85% for drinking water usage(H Kulkarni et al. 2015). The continuous depletion of groundwater levels(GWL) is becoming a significant concern in many agrarian regions of northwest India such as Delhi, Punjab and Rajasthan.This study focused on a few metropolitans and historical cities of Rajasthan, mainly in Sikar, Jaipur, and Jodhpur districts, where the Central Groundwater Board (CGWB) report shows groundwater depletion has been significant over the last two decades. The study areas in the eastern and western parts of Rajasthan are most susceptible to frequent droughts and dense populations and have much less than the average national rainfall.This research consists of twofold objectives to investigate the groundwater dynamics of the aquifer systems in those regions. First, we focus on understanding GW situations over the study areas using rainfall and suitable water-level data. Second, we investigate local scale surface deformation maps exploring Sentinel-1(S1) data of the European Space Agency (ESA) using an advanced multi-temporal Interferometric Synthetic Aperture Radar (MT-InSAR) technique. From 2000 to 2021,the precipitation data over Sikar, Jaipur, and Jodhpur districts show an average rainfall of 519.1 mm, 572.6 mm, and 337.81 mm, respectively, which are less than India’s national average, that is 1180 mm. Further, we analyzed 21 years of CGWB’s GW-level data from 2000 to 2021 over the three districts. We noticed a declining trend in water levels for all three regions during the study periods. The head-level data in Jaipur, such as Harmara, Astikalan, and Bhankrota, illustrate average GWL of 83.9 m, 71.59 m, and 70.35 m, respectively. In the Sikar district, Dhod, Ghana, and Rashidpura wellstations display an average GWL of 76.59 m, 69.3 m, and 83.1 m, respectively. In Jodhpur district, GWstations like Balarwa, Kapuria, and Khara have an average GWL of 116.13m, 77.31m, and 104.2 m, respectively. Analyzing further the local scale land motion, firstly, we carried out InSAR processing over the Sikar District, where 132 SAR acquisition of S1 with P34 descending orbital track considered from Sep 2016 to Dec 2021. We followed the Small BAseline Subset (SBAS) technique using the GMTSAR-InSAR tool by Sandell et al., 2011 for our data processing. The results exhibit 50 or 60 mm of land subsidence in the western and central parts of the Sikar district, whose displacement time series correlates well with the head-level decline. However, the ongoing investigation is being carried out by processing the S1 descending data from 2016 to 2021 over the Jaipur and Jodhpur districts and correlating InSAR results with the water-level change to understand the response of aquifer systems.