All the quantities occurring in right-hand sides of equations 2 and 3, besides TWS, were taken from GLDAS NOAH model (Rui, 2016); downloaded from appropriate subdirectory of http://hydro1.
The total canopy water storage values obtained from GLDAS (NOAH) had not been taken into consideration, because they were significantly smaller than other components.
Units of GWL and other GLDAS state components before differentiation are kg per square meter, which again is simplified to meters, TWS is in meters, too.
The computed value of [DELTA]S' can also be regarded as total water storage change, computed on the basis of GLDAS flux data corrected for groundwater level variations.
It was shown that groundwater changes computed on the basis of GRACE total water storage and stable GLDAS data (soil moisture and snow water equivalence) are consistent with the water balance determined from flux GLDAS variables (precipitation, evaporation, surface and subsurface run-off).