Groundwater Flow Dynamics and Storage Depletion in the North China Plain

The North China Plain (NCP) is one of the most important agricultural and economic regions of China and one of the most densely populated in the world. During the 1950s to 1960s, the shallow water table was 0-3 m below the land surface in most places. Increasing groundwater withdrawal since the 1970s; however, has caused continuing depletion in both shallow and deep aquifers. By the end of the 1990s, groundwater levels were declining at a rate of ~ 1 m/year in many intensive exploitation areas of NCP. In recent years, groundwater provides ~ 70% of total water supply. Recent field investigations have shown: (a) the maximum depth to the water table in the shallow aquifer has exceeded 65 m and the area with the water table 10 m or deeper is approximately 62,000 km², or 45% of the entire plain; and (b) the maximum head drop in the deep aquifer has reached 110 m and the area with the water level lower than the sea level is about 88,000 km², or 53% of the plain. A three-dimensional numerical flow model has been constructed to reproduce the groundwater flow dynamics and storage changes for the entire Quaternary aquifer from 1970 to 2008. Detailed water level measurements at 230 observation wells and historical water level contour maps were used to calibrate the transient flow model. Additional constraints were provided by flow budgets and groundwater age data. The model simulations indicate that a decrease in precipitation (~7% decrease in the 1990s compared to 1970s) and an increase in groundwater pumping are the primary causes for groundwater depletion in the NCP. The model results show that groundwater overexploitation exceeds 4 billion m³ annually. The groundwater flow model results are further compared and contrasted with the GRACE satellite data for the NCP.