Spatial Correlation Analysis of Land Subsidence and The Water Table Changes in Unconfined Aquifers Using Sentinel 1-SAR Image and Geographic Information Systems (Case Study: Semarang City – Indonesia)

Abstract

Groundwater has a very important role both in terms of environmental, social and economic. The consumption of groundwater continuously can affect the physical condition of the environment such as land subsidence, especially in Semarang City. The spatial correlation of land subsidence and water table changes was analyzed in this study using remote sensing and geographic information systems. PS-InSAR method is used to process Sentinel-1 SAR image satellite to get the result of land subsidence during in 2014-2017. The annual average of vertical land subsidence in Semarang City, with the range 0 ± 3.4 cm to 4.5 ± 3.4. The spatial relation between the land subsidence and the water table decreased is obtained using the rules of the spatial correlation matrix. The study area was dominated by a very high correlation with the percentage (47.58%), which located in several areas in Genuk District, Tembalang District, Pedurungan District, Tugu District and Mijen District. The potential of groundwater in unconfined aquifers in Semarang City is nihil potential and low potential of groundwater quality. The very high correlation between land subsidence and water table decreased, which located in the low potential of groundwater in unconfined aquifer mostly located in Tembalang District.