Monthly Dynamic Groundwater Estimation using GRACE over Indonesia

Abstract

Indonesia is an archipelago with tropical climatic conditions, and part of it has arid areas. Monitoring groundwater dynamics effectively and efficiently is one of the challenges in a large area. GRACE is the Geodesy satellite that collects the sub-surface data. GRACE data is one of the gravity anomaly data that can be used for groundwater dynamics detection. Monthly groundwater monitoring can be used to determine the dynamic pattern of terrestrial water storage. It can be used as a parameter for the detection and prediction of drought in a large area. This study aims to model Indonesia's monthly groundwater levels based on gravity anomaly with GRACE satellite data. Anomaly gravity in GRACE's data is the main parameter in monitoring groundwater dynamics. Based on the results of monitoring during January-December 2020, three groundwater conditions were obtained in Indonesia. These conditions always have high groundwater potential, areas with diverse groundwater dynamics, and low groundwater areas. This low groundwater condition occurs in arid areas. The dynamic groundwater pattern occurred in the same month and had a similar pattern every season observed from 2002-2020. For example, the East Nusa Tenggara region has nine months of low groundwater potential. The potential and prediction of drought can be anticipated following the results of monitoring groundwater dynamics. Monitoring and predicting drought by predicting groundwater dynamics using GRACE's data can be an efficient and effective alternative for mapping, especially in Indonesia's vast and water-dominated territory.