Groundwater storage variations in the North China Plain using multiple space geodetic observations
Résumé
Water storage and pressure variations in the subsurface generate measurable gravity changes and surface displacements. This study presents the joint interpretation of GRACE and GPS/InSAR observations to better understand shallow and deep groundwater storage (GWS) variations associated with unsustainable pumping and impact of climate variability in the North China Plain (NCP). On seasonal timescales, GRACE-derived GWS variations are well explained by the combined effect of groundwater abstraction due to anthropogenic irrigation activities and groundwater recharge from natural precipitation. Interannual GWS variations in the NCP detected by GRACE is consistent with precipitation anomalies. During the drought years (e.g., 2002 and 2014), significant GWS depletion is detected by GRACE satellites. The GRACE-derived GWS variation rate is -8.0 ± 1.5 km3/yr during 2002-2014, which is significantly larger than the estimate from phreatic monitoring well observations. The difference between them indicates the significant GWS depletion in the confined deep aquifers of the NCP, generating large subsidence rates, which has been largely underestimated up to now. The GWS variation rate in deep aquifers estimated from GPS/InSAR observations can explain the difference between the GWS depletion rate from GRACE and that from well observations. Both GRACE and surface displacement offer significant potential to better understand water redistribution in shallow and deep aquifer systems of the NCP.