Regional Terrestrial Water Storage Changes in the Yangtze River Delta over the Recent 20 years

Abstract. Monitoring changes in regional terrestrial water storage (TWS) and groundwater storage (GWS) is important for effectively managing water resources. Here, we investigate the TWS and GWS changes in the Yangtze River Delta using the GRACE/GRACE-FO mascon solutions, GLDAS NOAH models and in situ groundwater level changes from monitoring wells over the period of April 2002 to December 2022. The results show that the regional mean TWS change rate of the entire Yangtze River Delta is 0.62±0.10 mm/year, at 0.47±0.07 mm/year for the GWS component and 0.15±0.08 mm/year for the other components, which includes soil moisture, snow water and surface water change derived from the GLDAS NOAH models. At the basin scale, significant positive trends existed in water storage in Shanghai and Zhejiang Provinces; however, relatively small negative trends existed in Jiangsu and Anhui Provinces, which was confirmed by the spatial distributions of areas with linear trends. After comparing the estimated GWS change with the in situ groundwater level change from thirteen monitoring wells, we concluded that the groundwater levels in Shanghai and Zhejiang Provinces slightly recovered over the last 20 years and that this trend will continue in the coming years, mainly due to the sustainable water resource management policies of the local governments.