Work

Temporal and spatial variability of groundwater storage derived from downscaled GRACE data in the transboundary Bug River Basin (Poland–Ukraine–Belarus border region)

Year: 2025

Type: article

Abstract: This study presents an enhanced approach for estimating groundwater storage (GWS) dynamics using downscaled Gravity Recovery and Climate Experiment (GRACE) data combined with Global Land Data Assimilation System (GLDAS) outputs in the transboundary Bug River Basin. We applied three innovations to improve satellite-based GWS estimation. First, we applied the random forest (RF) algorithm to downscale GRACE terrestrial water storage (TWS) data to 0.1° × 0.1° resolution, using precipitation, evapotranspiration, runoff, and soil moisture as predictors. Second, we introduced a novel cumulative component to the GLDAS-based TWS change indicator, representing vadose-zone water equivalent, which depends on groundwater level (GWL) depth. This adaptation accounted for hydrodynamic conditions by extending the accumulation period with increasing GWL depth, effectively reducing phase shifts and temporal delays relative to the in-situ GWS observations common in prior studies. Third, satellite-based GWS estimates were calibrated using in-situ groundwater measurements combined with RF and kriging. The proposed approach significantly improved consistency between satellite-derived and in-situ GWS (correlation coefficients between 0.66 and 0.95), enhancing the reliability of groundwater monitoring. The GWS seasonal variability and amplitude were found to strongly depend on vadose zone properties and GWL depth. Despite an overall decline in total TWS, GWS in the Bug River Basin remained stable, reflecting system resilience to climatic fluctuations. Our methodology enhances groundwater monitoring and forecasting in transboundary catchments and enables the development of continuous changes in GWS in time and space, which is particularly important for regions with a sparse network of in-situ observations. • RF downscaling improved TWS GRACE resolution to 0.1° × 0.1°. • ΔTWS GLDAS accumulation index accounted for vadose-zone moisture dynamics. • Satellite-based GWS was calibrated with in-situ data via RF method and kriging. • GWS in the BRB shows stability despite declining TWS. • The new method improved the correlation between satellite-derived and in-situ GWS.

Source: The Science of The Total Environment

DOI: 10.1016/j.scitotenv.2025.181023

Authors: Tatiana Solovey, Justyna Śliwińska-Bronowicz, Rafał Janica, Anna Stradczuk, Agnieszka Brzezińska

Institutions: Polish Geological Institute, Centrum Badań Kosmicznych

Language: English

Topic: Geophysics and Gravity Measurements

Subfield: Oceanography

Field: Earth and Planetary Sciences

Domain: Physical Sciences

SDGs: Clean water and sanitation, Climate action

Open Access status: hybrid

Estimated APC paid: $4,250