GRACE-derived spatiotemporal changes of terrestrial water storage in the major plateaus of China

Changes in terrestrial water storage (TWS) significantly impact water resource regulation in the major plateaus of China (MPC). Traditional monitoring methods are limited by high costs and sparse site distribution, restricting large-scale and high-resolution assessments. The Gravity Recovery and Climate Experiment (GRACE) and its follow-on mission offer an effective approach for TWS observation in these areas. This study examines the spatiotemporal features of TWS in MPC from 2002 to 2022 by recovering low-degree signals through coefficient substitution, restoring high-degree signals via combined filtering, and interpolating missing data using Singular Spectrum Analysis (SSA). Key findings reveal a TWS change rate of −0.1 cm/year in the MPC, with semi-annual and annual amplitudes of 0.7 cm and 2.3 cm, respectively, peaking between September and October. TWS variations in the MPC are largest in the Qinghai-Tibet Plateau (QTP) and this dominant signal tends to mask the trends in other plateau regions. Among these, the Yunnan-Kweichow Plateau (YKP) is exhibiting a gradually increasing TWS trend. In the western YKP, TWS declines due to concentrated rainfall, while in its eastern regions, a combination of reduced seasonal precipitation and water migration contributes to an overall upward trend. These findings provide critical insights for regional water resource management and policy formulation.