Mutual Consistency of Groundwater Storage Changes Derived From GRACE and From Baseflow Recessions in the Central Yangtze River Basin

A comparison is presented between groundwater storage trends derived from Gravity Recovery and Climate Experiment (GRACE) satellite measurements and trends derived from unregulated river baseflow observations in 19 catchments in tributaries of the Central Yangtze River. The two sets of trends are well correlated with a coefficient of r = 0.64, but the baseflow-derived trends were found to be on average about 33% smaller than those based on the GRACE measurements. Although other factors undoubtedly play a role, the difference in trend magnitudes of the two sets of trends is concluded to be mainly due (i) to remaining uncertainties and complexities in GRACE data processing and (ii) to the likely gradual shrinking of the contributing catchment areas during the baseflow recession process. The present findings should be useful in extending GRACE measurements to longer periods on the basis of long-term streamflow measurements and in recovering missing data.