Groundwater Storage Changes within Europe: A Constrained Bayesian Integration of GRACE(-FO) Data into the W3RA Model

his dataset provides monthly estimates of groundwater storage change (GWS) across Europe at an effective spatial resolution of approximately 10 km, generated using an extended Constrained Bayesian (ConBay) data integration framework.
The ConBay framework integrates satellite gravimetric observations from GRACE (2003–2017) and GRACE-FO (2018–present) with outputs from the W3RA hydrological model, while additionally constraining surface soil moisture states using independent observations from the ESA Climate Change Initiative (ESA CCI) soil moisture product (v09.1). This multi-source constraint improves the physical consistency between modeled and observed terrestrial water storage components and reduces equifinality in groundwater partitioning.
To ensure spectral consistency, W3RA total water storage fields are transformed into the spectral domain and filtered using GRACE-consistent operators prior to assimilation. After Bayesian updating, residual components are reintroduced to enable physically coherent spatial downscaling of terrestrial water storage changes. ESA CCI soil moisture observations are incorporated as an independent constraint on surface soil moisture variability, improving consistency between surface and subsurface water storage dynamics.
The resulting GWS estimates preserve the large-scale information content of GRACE while resolving sub-basin to regional-scale groundwater variability. Validation against in-situ groundwater level observations demonstrates improved representation of groundwater dynamics compared to existing gravity-based products, particularly in regions with complex hydrogeology and strong land–atmosphere coupling.
Key characteristics
Spatial coverage: EuropeSpatial resolution: ~10 kmTemporal resolution: MonthlyTime span: 2003–present (GRACE and GRACE-FO eras)Variable: Groundwater storage change (GWS)Units: [meter equivalent water height]Constraints: GRACE/GRACE-FO terrestrial water storage change; ESA CCI surface soil moistureIntended use
This dataset is intended for research applications including continental-scale groundwater monitoring, hydro-climatic variability and drought assessment, model evaluation, and digital-twin development. Users should consider the intrinsic spatial smoothing of GRACE observations and the uncertainty characteristics provided with the dataset.

Citation
For the technical details, users of this dataset are requested to cite the associated publication "Exploring the Dynamics of Deep Stored Water Resources within Europe by Developing a 10-km resolution Groundwater Estimate for a Digital Twin of the Terrestrial Water Cycle".
For the dataset itself, please cite the Figshare information.