Geodetic and hydrological measurements reveal the recent acceleration of groundwater depletion in North China Plain

Abstract

As one of the most important agricultural bases in China, the North China Plain (NCP) has experienced serious groundwater depletion. However, estimates of groundwater depletion rates in NCP differ considerably from one another due to different datasets and methods used in the estimation. To get a better estimate of the groundwater depletion and to reveal the recent groundwater changes in NCP, we first merge Gravity Recovery and Climate Experiment (GRACE) mass concentration (mascon) solutions from different organizations and soil moisture from different land surface models to yield unified mascon solutions and soil moisture estimates. We then estimate the groundwater changes by subtracting the unified soil moisture and surface water storages in the major reservoirs in NCP from the unified mascon solutions. Results show that the groundwater storage in NCP depleted at a rate of 1.7 ± 0.1 cm/yr from 2004 to mid-2016 but this depletion accelerated to 3.8 ± 0.1 cm/yr from mid-2013 to mid-2016. Ground-based water table data show a consistent groundwater depletion rate (−3.9 ± 0.3 cm/yr from mid-2013 to mid-2016) with the GRACE results. We also analyze the land subsidence in NCP by using 116 Global Positioning System (GPS) sites and depict the accelerated land subsidence and expanded subsidence funnels since 2013, which is consistent with the groundwater depletion. All these point to a strong acceleration in groundwater depletion in NCP since mid-2013. Land surface model outputs suggest a precipitation decline from 2013 to 2016, which caused a decline in soil moisture content and surface water storage. This drought forced people to exploit more groundwater to compensate the surface water shortage and thereby led to the accelerated groundwater depletion.