Abstract:
The severe shortage of water resources is a critical ecological and environmental challenge faced by the Beijing–Tianjin–Hebei region, impeding the implementation of regional coordinated development strategies. Terrestrial water storage (TWS) changes profoundly affect the distribution and supply of water resources. Therefore, comprehensively understanding the characteristics and drivers behind TWS and its components is crucial for improving regional water resource management and achieving the optimal allocation of these resources, ultimately supporting sustainable utilization of regional water resources. At present, the changes in water storage and its components and the impact of natural and human factors within the Beijing–Tianjin–Hebei region are insufficiently understood. This paper leverages data from the GRACE (Gravity Recovery and Climate Experiment) and the GLDAS (Global Land Data Assimilation System) to analyze the temporal and spatial change characteristics of TWS and its components over the past 20 years (2002–2021). Additionally, it analyzes the factors influencing water storage changes from a water cycle perspective, incorporating data on precipitation, evapotranspiration, runoff, and human water consumption. The results reveal the following: (1) TWS and groundwater storage in Beijing, Tianjin, and Hebei have exhibited significantly declining trends, with trend coefficients of −0.71, −0.84, and −1.26 cm/a for TWS and −1.12, −1.01, and −1.55 cm/a for groundwater storage, respectively from 2002 to 2021. By contrast, soil water storage presented a notable increasing trend. (2) Groundwater storage changes in Beijing, Tianjin, and Hebei closely align with those of their respective TWS, demonstrating correlation coefficients of 0.8 or higher. In addition, the trends of other components are increasing, which is opposite to the trend of TWS. This indicates that the significant decrease in groundwater storage is the main cause of TWS reduction in the Beijing–Tianjin–Hebei region. (3) Increased precipitation has positively influenced TWS across the three provinces/cities, while the increase in evapotranspiration and runoff levels negatively contributes to TWS. The interplay of climate/hydrological factors has led to TWS gains in Beijing and Tianjin but declines in Hebei. The contribution rates of climate change to TWS changes are 23.60%, 33.95%, and 26.99% for Beijing, Tianjin, and Hebei, respectively, while human activities account for 76.40%, 66.05%, and 73.01%, respectively. This indicates that TWS declines are mainly influenced by human activities. (4) The significant reduction in groundwater storage directly stems from the massive exploitation of groundwater caused by human activities, highlighting the importance of stringent water use management for sustainable water resource utilization in the Beijing–Tianjin–Hebei region. This research offers valuable data support for scientifically grasping the spatiotemporal changes and impact mechanisms of water reserves in the Beijing–Tianjin–Hebei region, offering a theoretical basis for the effective management of water resources in the region.