Satellite signal shows storage-unloading subsidence in North China

Abstract. Worsening water storage depletion (WSD) contributes to environmental degradation, land subsidence and earthquake and could disrupt food production/security and social stability. There is need for efficient water use strategies in North China, a pivotal agrarian, industrial and political base in China with a widespread WSD. This study integrates satellite, model and field data products to investigate WSD and land subsidence in North China. In the first step, GRACE (Gravity Recovery and Climate Experiment) mass rates are used to show WSD in the region. Next, GRACE total water storage (TWS) is corrected for soil water storage (SWS) to derive groundwater storage (GWS) using GLDAS (Global Land Data Assimilation System) data products. The derived GWS is compared with GWS obtained from field-measured groundwater level to show land subsidence in the study area. Then GPS (Global Positioning System) data of relative land surface change (LSC) are used to confirm the subsidence due to WSD. A total of ~ 96 near-consecutive months (January 2002 through December 2009) of datasets are used in the study. Based on GRACE mass rates, TWS depletion is 23.76 ± 1.74 mm yr⁻¹ or 13.73 ± 1.01 km³ yr⁻¹ in the 578 000 km² study area. This is ~ 31 % of the slated 45 km³ yr⁻¹ water delivery in 2050 via the South–North Water Diversion Project. Analysis of relative LSC shows subsidence of 7.29 ± 0.35 mm yr⁻¹ in Beijing and 2.74 ± 0.16 mm yr⁻¹ in North China. About 11.53 % (2.74 ± 0.18 mm or 1.58 ± 0.12 km³) of the TWS and 8.37 % (1.52 ± 0.70 mm or 0.88 ± 0.03 km³) of the GWS are attributed to storage reductions accompanying subsidence in the region. Although interpretations of the findings require caution due to the short temporal and large spatial coverage, the concurrence of WSD and land subsidence could have adverse implications for the study area. It is critical that the relevant stakeholders embark on resource-efficient measures to ensure water availability, food security, ecological sustainability and social stability in this pivotal region.