MODELING GROUNDWATER FLOW AND STORAGE IN THE NORTH CHINA PLAIN

The North China Plain (NCP) is one of the most important agricultural and economic regions of China and has a high population density. The Quaternary aquifer of the NCP is one of the world’s largest aquifer systems and supports enormous groundwater exploitation. In recent years, groundwater provides nearly 70% of total water supply of this region to support grain production, rapid economic development and population growth. Increasing groundwater demands since the 1970s have caused continuing groundwater depletion associated with water level declines in both shallow and deep aquifer units. In this study, we developed a numerical model for the NCP using MODFLOW to simulate the groundwater dynamics and storage change for the entire Quaternary aquifer. In this model, the Quaternary aquifer was divided into three layers representing the shallow, intermediate and deep aquifer systems. We first constructed a steady-state model to reproduce the pre-development groundwater conditions in the 1970s. We then developed a transient flow model to simulate the development of cones of depression and related aquifer storage change from the 1970s to present. Detailed water level measurements at observation wells and historical water level contour maps were used to calibrate the transient model using both trial-and-error and nonlinear regression methods. Additional constraints were provided by flow budget and groundwater age data. The model results show the groundwater overexploitation exceeds 4 billion cubic meters annually. The numerical groundwater model developed in this study provides an invaluable tool for assessing the impacts of various climate change scenarios and management options on the sustainability of groundwater resources in the region.