Grace-Derived Groundwater Depletion from Both Shallow and Deep Aquifers within North China Plain

Abstract:

This study explores the capability of GRACE to detect groundwater storage variations in the two sub-regions in the North China Plain (NCP): the Piedmont Plain (PP, mainly shallow unconfined-aquifers) and East-Central Plain (ECP, mainly deep confined-aquifers), both of which have the areas smaller than the typical GRACE footprint (~200,000 km2). Our assessments were based on the forward modeling method using GRACE release-05 (RL-05) solutions, hydrological models (2003-2013), and in situ groundwater level measurements (2005~2010) from both shallow and deep aquifers. Results show that the GRACE-derived GWS variation in the PP experienced a severe depletion of GWS (-46.5±6.4 mm yr-1) over the past decade, nearly 3 times that of the ECP (-16.9±2.1 mm yr-1). There were apparent renewal episodes of GWS (e.g. since 2010) in PP, which may reveal the high replenishing capability of unconfined aquifers. Despite the lower depletion rate, the deep GWS with poor recoverability may have been overexploited. The depletion rate (-16.9±2.1 mm yr-1) exceeded the maximum allowable depletion rate (~12.4 mm yr-1) based on a 50-year groundwater budget.