Scaling methods of leakage correction in GRACE mass change estimates revisited for the complex hydro-climatic setting of the Indus Basin

Abstract. Total water storage change (TWSC) reflects the balance of all fluxes in a hydrological system. The Gravity Recovery and Climate Experiment/Follow-On (GRACE/GRACE-FO) monthly gravity field models, distributed as spherical harmonic (SH) coefficients, are only means observing this state variable. well-known correlated noise these observations requires filtering, which scatters actual mass changes from their true locations. This effect is known leakage. study explores traditional basin grid scaling approaches, develops novel frequency-dependent for leakage correction GRACE TWSC unique, basin-specific assessment Indus Basin. We harness characteristics significant heterogeneity Basin due to climate human-induced physical nature schemes. most recent WaterGAP (Water Global Assessment Prognosis) hydrology model (WGHM v2.2d) with its two variants, standard (without glacier changes) Integrated (with changes), used derive factors. For first time, we explicitly show inclusion or exclusion on gridded inferences were validated detailed simulation environment designed using WGHM fields corrupted GRACE-like errors full error covariance matrices. find that outperforms both Basin, where different frequencies localized. Grid can resolve trends loss groundwater but fails recover small seasonal signals trunk Indus. Frequency-dependent provide robust estimate cycle practical applications such regional-scale availability assessments. Apart developments insights into approach, our encourages regional scale users conduct specific assessments interest.