The Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On twin satellites have revealed mass variation over time by measuring Earth's gravity field anomalies since 2002. These variations can be interpreted as changes in water storage on and beneath the earth's surface. The water storage anomaly, also known as the Terrestrial Water Storage Anomaly (TWSA), has been utilized successfully to estimate a Flood Potential Index (FPI). The GRACE-based FPI (GRACE-FPI) is a good indicator of when a region is at risk of flooding. However, the GRACE data are limited by low spatial resolution, which has limited applicability to study areas smaller than 200,000 km2. Since the change in storage derived from the traditional water budget equation has the same physical meaning as the GRACE TWSA, we hypothesize there are similarities in their derived FPIs. In this study, we propose another index, known as the Water Budget–based FPI (WB-FPI), which is derived using higher spatial resolution hydrological datasets and could produce similar but higher-resolution results than the GRACE-FPI. When combined with the GRACE-FPI, the index could be valuable in providing flood prediction estimates on a catchment scale. Additionally, a combination of both indices could significantly reveal hydrological details for small basins. Both the GRACE-FPI and WB-FPI were applied to a case study of the flood potential of the U.S. Mississippi River Basin. Our study reveals good correlation between the resampled GRACE-FPI and WB-FPI using the Nash-Sutcliffe efficiency index to compare application efficacy.

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