A dynamical downscaling method of groundwater storage changes using GRACE data

Abstract

Study region: The Northwest inland region of China. Study focus: The use of Gravity Recovery and Climate Experiment (GRACE) satellite data for assessing groundwater storage changes (GWSC) is rapidly expanding; however, dealing with such low spatial resolution data is always a challenge. In the present study, a dynamical downscaling method based on groundwater flow processes was proposed to simulate GWSC. Firstly, a hypothetical model constructed by MODFLOW package used to evaluate the efficiency of the developed model. Then, a part of the northwest inland region of China was taken as a real example to verify the applicability of the model. Finally, the downscaled results are used to estimate the groundwater storage changes in the study area. New hydrological insights for the region: The spatiotemporal change of GWSC from the proposed model in a hypothetical conceptual model matched well with those from the MODFLOW package. The average correlation coefficient between downscaled GWSC and observed groundwater level is over 0.54, and downscaled GWSC showed the reasonable heterogeneity in the study area. From 2008–2011, the area with a decline in groundwater storage accounted for about 12% of the total area, while it increased to 21.8% from 2012 to 2016. The proposed model has the potential to be applied for the large-scale evaluation of GWSC and to improve the understanding of GWSC in remote areas.

Keywords

• GRACE
• Dynamical downscaling
• Groundwater storage model
• Model calibration
• Uncertainty analysis