Evolution of groundwater level in the North China Plain in the past 40 years and suggestions on its overexploitation treatment

As one of the three great plains in China, North China Plain is also one of the main grain-producing areas. As Beijing-Tianjin-Hebei coordinated development zone and the Xiongan New Area are both located in the region, its geographical location is extremely important. Groundwater is the main source of water supply in North China Plain, accounting for about 70% of the total water supply. The increasing exploitation of groundwater since the end of 1970s enables it to be in a state of serious overexploitation for a long time, forming a huge groundwater depression cone leading to a series of environmental and geological problems such as land subsidence, ground cracks, wetland degradation, seawater intrusion, etc., restricting the sustainable development of society and economy. The analysis and research on the evolution of groundwater level can provide support for the treatment of groundwater overrun and the restoration of falling funnels. Based on the high-density simultaneous measurement of groundwater level from 2019 to 2020 and historical groundwater level data, the flow field and funnel distribution of the current groundwater level in 2020 were clarified, and the variation characteristics of the groundwater level in the last 40 years were systematically analyzed. The results show that the shallow groundwater in the eastern and western parts of the North China Plain develops in different ways, the shallow groundwater in the west of the plain continued to decline rapidly from the 1980s to 2014 with a cumulative decline of 20-60 meters. The water level in the edge of alluvial and diluvial fan in the piedmont of Taihang Mountain declined the most. After the South-to-North Water Transfer Project began supplying water in 2014, water levels in major western piedmont cities stopped falling and rose. The groundwater level in the central and eastern regions fluctuated naturally. From the 1980s to 2014, the deep groundwater level showed a general downward trend, and the water level in the central and eastern regions dropped the most, reaching 40-90 m accumulatively. After 2014, the deep groundwater level in urban areas and agricultural areas developed differently, and the water level in urban areas recovered obviously, while the surrounding agricultural areas still showed a rapid downward trend. Additionally, based on the analysis of groundwater evolution, aiming at the balance of groundwater mining and recharge and water level recovery, some suggestions are put forward to carry out the research on the threshold of target water level for the prevention and control of overexploitation areas, formulate the groundwater abatement and recharge scheme, and optimize the groundwater level monitoring network. The research results are of great significance to support the accurate management of groundwater overexploitation in the North China Plain, the restoration of groundwater depression cone, and the rational development and management of groundwater resources.