Regional water storage changes in the Yangtze River Delta over the past 20 years

Accurately estimating and interpreting the spatiotemporal changes of regional water storage under climate warming are of great value for formulating regional adaptive water management strategies.The Yangtze River Delta, with about 4 % of China's national land area (including Shanghai, Jiangsu, Zhejiang, and Anhui provinces), generates nearly one-fourth of the country's total economic gross domestic product.In this study, we estimate terrestrial water storage (TWS) and groundwater storage (GWS) changes in the Yangtze River Delta from April 2002 to January 2025 by integrating GRACE/GRACE-FO solutions, GLDAS land surface model outputs, groundwater level observations, coal mining records, and provincial water resource bulletins.The results show that GWS variations dominated regional TWS changes, with the linear trends of 0.68±0.12mm/year (GWS) and 0.88±0.17mm/year (TWS) after coal mining correction.Marked spatial heterogeneity exists: Shanghai and Zhejiang show strong positive TWS trends (4.89±0.16 and 3.68±0.22mm/year, respectively), driven by groundwater recovery under strict abstraction controls and artificial recharge; conversely, Jiangsu and Anhui exhibit slight TWS declines, attributed to non-groundwater loss and soil moisture reduction, respectively, with coal mining contributing to local depletion.These subregional values, particularly those for Shanghai, should be interpreted as indicative GRACE-footprint-scale estimates rather than locally precise values.Groundwater level data from monitoring wells corroborate these patterns, with significant increases in Shanghai and Zhejiang and decreases in northern Anhui and Jiangsu.