Analysis of terrestrial water storage variations in South Korea using GRACE satellite and GLDAS data in Google Earth Engine

With the requirement of a macroscopic approach to understanding the relationship between water resources and hydrological phenomena, such as severe droughts under climate change, this study investigates South Korea's long-term terrestrial water storage (TWS) using GRACE satellite data. A detailed analysis of water balance in TWS, based on the GLDAS model outputs in Google Earth Engine, reveals the following results: (1) TWS anomaly shows an average decrease of -33.5 mm year-1 from 2003 to 2016; (2) spatial shifts in TWS anomaly (-1.176 to -0.424 cm) unveil regional water storage dynamics, indicating negative temporal slope changes per grid cell (-0.393 to -0.225); (3) contributions of precipitation to TWS are not always straightforward, due to runoff inefficiencies affecting water storage and groundwater; (4) accessible water, integrating surface water and groundwater linked only to the shallow layer's soil moisture, constrains deep groundwater accounting, emphasizing the need for local groundwater surveys in further research.