Changes in groundwater levels across China from 2005 to 2016

Groundwater provides perennial, ubiquitous and high-quality freshwater supplies for humanity globally. Difficulties in the collection and collation of groundwater records have hindered our understanding of large-scale groundwater dynamics. This study collected groundwater level depth (GLD) records from 909 groundwater wells across China and the spatiotemporal changes in GLD were investigated in unconfined and confined aquifers from 2005 to 2016 nationally. The GLD distributions were highly heterogeneous, with average (standard deviation) GLDs of 11.9 (20.3) and 21.6 (26.4) m in unconfined and confined aquifers, respectively. From 2005 to 2016, the GLDs decreased significantly over the energy-limited region due to increased precipitation but increased significantly over the water-limited region due to high groundwater abstraction. The GLD changes in confined aquifers were larger than those in unconfined aquifers due to the smaller storativity in confined aquifers. The correlations between the GLDs and GRACE total water storage (TWS) anomalies over the water-limited region were higher than those over the energy-limited region, indicating that groundwater storage contributed more to TWS over arid areas than humid areas. This study highlights the increasing groundwater storage in the energy-limited region and the decreasing groundwater storage in the water-limited region, i.e., enhanced regional differences in groundwater resources. The results improve our understanding of groundwater dynamics in different aquifers and climatic conditions and hence advance robust groundwater management and policy development in China.