Water budget variation, groundwater depletion, and water resource vulnerability in the Haihe River Basin during the new millennium

Water resources are one of the critical areas of concern for the Haihe River Basin (HRB) in North China. With continuous improvements in observation and remote sensing techniques since 2000, multi-source information has allowed the comprehensive investigation of the evolution of water resources. Datasets were synthesized from a range of sources, such as ground-based measurements of precipitation, groundwater table depth (WTD), Gravity Recovery and Climate Experiment (GRACE) satellite-based terrestrial water storage (TWS) products, the Global Land Data Assimilation System, the Climatic Research Unit, and the Water Resources Bulletin (WRB) datasets. From a meteorological perspective, the HRB has become wetter since 2000 according to the selfcalibrated Palmer drought severity index, with the results exhibiting an increase in precipitation. However, warming has also caused more evapotranspiration. The significant decreasing trend of GRACE-based TWS changes indicated that the HRB water resources were under huge stress, particularly in the plain area. Water stress was primarily caused by high levels of human water withdrawals as shown by the WRBs. Groundwater storage has been severely depleted than the TWS at a rate of -11.16 mm/yr. This correlated well with the monitored WTD. Water resource vulnerability was severe in most subbasins of the HRB, particularly in areas with a large population. According to the GRACE Follow-On products, water storage depletion in the HRB continued up to 2020, necessitating a water crisis response system and sustainable water development in the future.