Geospatial Analysis of Groundwater Usage Level Corresponding to Land Displacement Trend Derived from Time-Series SAR Interferometry and GNSS Measurements

Concerning monitoring the water resource, the impact of the extensive groundwater extraction can be assessed based on subsidence. Geospatial analysis was performed by integrating spatial information of the groundwater usage level with the distribution of land displacement indication derived from an advanced time-series SAR Interferometry (InSAR) analysis of Persistent-Scatterer (PS) and Small Baseline Subset (SBAS) methods in Bali Island, Indonesia.
The data source consists of well data and satellite data.
(1) The monitoring well data contains a database of well locations, capacities, and percentage of water supply (service coverage). The information was collected from the River Basin Agency of Bali Penida (BWS-BP), Public Works Service (DPU) in Bali Province, Regional Public Works Service (DPU), and Regional Drinking Water Agency (PDAM). Based on the data collected in 2017, the groundwater usage levels were categorized into high (> 50 l/s), moderate (25 – 50 l/s) and low (<25 l/s).
(2) The satellite data utilized to extract information of land subsidence, i.e., SAR data of Sentinel-1A, Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM) data, and Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) data. The entire data processing was performed using open-source computer software, i.e., InSAR processing system of GMT5SAR, RTKLIB with GNSS data, and QGIS for spatial data extract and mapping.
The results pointed out the correlation between groundwater usage and subsidence in the area. Furthermore, the information can be employed as a reference to determine vulnerabilities of the resource development strategies.