Subregional-scale groundwater depletion detected by GRACE for both shallow and deep aquifers in North China Plain

This study explores the capability of Gravity Recovery and Climate Experiment (GRACE) to detect heterogeneous groundwater storage (GWS) variations in two subregions of the North China Plain: the Piedmont Plain (PP, ∼54,000km², mainly exploiting shallow groundwater) and East Central Plain (ECP, ∼86,000km², mainly exploiting deep groundwater). Results show that the GWS anomalies estimated from GRACE data (2003-2013) agree well with those estimated from in situ observations (2005-2010) for both PP (R²=0.91) and ECP (R²=0.75). The shallow GWS (2003-2013) in PP declines faster (-46.5±6.8mm/yr) than the deep GWS in ECP (-16.9±1.9mm/yr). However, the shallow GWS in PP recovered more quickly especially during the 2008-2011 drought period. Despite its lower magnitude, the GRACE-derived GWS depletion in ECP reveals the overexploitation of deep GWS. This study demonstrated that the heterogeneous GWS variations can potentially be detected by GRACE at the subregional scale smaller than the typical GRACE footprint (200,000km²). Key Points GRACE has the potential to detect subregional heterogeneous GWS depletion in NCP Shallow GWS in the Piedmont Plain declines faster but also recovers more quickly GRACE data reveal the overexploitation of deep GWS in the East Central Plain