Central and Southern Europe is undergoing a drying trend driven by increased evapotranspiration and rising air temperatures, even though precipitation levels remain stable. In the Bug River Basin, GRACE observations indicate that total water storage (TWS) declined at a rate of 8.8 ± 5.2 mm/year between 2012 and 2023. To validate this trend, we analysed spatial and temporal discrepancies between TWS-GRACE and water budget-based estimates (TWS-WB). Using ensemble data assimilation techniques, we integrated hydrometeorological data with TWS-GRACE. Regression models developed for TWS simulation were employed to adjust TWS-GRACE estimates. The results demonstrate that TWS fusion effectively mitigates uncertainties in TWS-GRACE caused by its low spatial and temporal resolution. Correlation analysis between TWS-fusion and TWS-GRACE identified errors in GRACE solutions and commonly used autoregressive methods for filling data gaps. Our findings show that model developed in this study significantly improved alignment between TWS-GRACE and TWS-WB, reducing RMSE from 34.7 to 14.9 mm/month. The proposed data fusion approach based on combining GRACE observations with precipitation, evapotranspiration, and runoff data, offers a viable alternative for extending TWS-GRACE time series beyond the GRACE observational period. Additionally, our research provides valuable insights for downscaling GRACE data and addressing challenges in spatial and temporal interpolation, which remain critical in water resource studies.
Global Navigation Satellite System (GNSS) vertical displacements measuring the elastic response of Earth's crust to changes in hydrologic mass have been used to produce terrestrial water storage change (∆TWS) estimates for studying both annual ∆TWS as well as multi‐year trends. However, these estimates require a high observation station density and minimal contamination by nonhydrologic deformation sources. The Gravity Recovery and Climate Experiment (GRACE) is another satellite‐based measurement system that can be used to measure regional TWS fluctuations. The satellites provide highly accurate ∆TWS estimates with global coverage but have a low spatial resolution of ∼400 km. Here, we put forward the mathematical framework for a joint inversion of GNSS vertical displacement time series with GRACE ∆TWS to produce more accurate spatiotemporal maps of ∆TWS, accounting for the observation errors, data gaps, and nonhydrologic signals. We aim to utilize the regional sensitivity to ∆TWS provided by GRACE mascon solutions with higher spatial resolution provided by GNSS observations. Our approach utilizes a continuous wavelet transform to decompose signals into their building blocks and separately invert for long‐term and short‐term mass variations. This allows us to preserve trends, annual, interannual, and multi‐year changes in TWS that were previously challenging to capture by satellite‐based measurement systems or hydrological models, alone. We focus our study in California, USA, which has a dense GNSS network and where recurrent, intense droughts put pressure on freshwater supplies. We highlight the advantages of our joint inversion results for a tectonically active study region by comparing them against inversion results that use only GNSS vertical deformation as well as with maps of ∆TWS from hydrological models and other GRACE solutions. We find that our joint inversion framework results in a solution that is regionally consistent with the GRACE ∆TWS solutions at different temporal scales but has an increased spatial resolution that allows us to differentiate between regions of high and low mass change better than using GRACE alone.
more » « less- Award ID(s):
- 2054160
- PAR ID:
- 10374466
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Solid Earth
- Volume:
- 127
- Issue:
- 3
- ISSN:
- 2169-9313
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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