Multi-decadal water budget dynamics of the Great Gibe river basin using google earth engine and SWAT

ABSTRACT Graphical abstract summarizes multi-decadal water budget components, remote sensing data, and annual hydrological trends in Ethiopia's Great Gibe River Basin. Climate change is intensifying pressure on water systems in data-scarce regions where a clear understanding of long-term water budget dynamics is challfenging. This study decodes the temporal and spatial variability of water budget components in Ethiopia's Great Gibe River Basin through multi-decadal analysis. The aim was to improve the understanding of climate-driven hydrological variability and support climate-resilient water resource management. We integrated Google Earth Engine, remote sensing datasets, and the Soil and Water Assessment Tool to quantify precipitation, evapotranspiration, soil moisture, runoff, and storage changes within a closed water balance framework. The results showed that while precipitation and runoff exhibited substantial interannual variability (CV > 23%), evapotranspiration remained the dominant loss component, accounting for 45.1% of the water budget. Basin storage displayed long-term equilibrium (ΔS ≈ 0), indicating no significant multi-decadal accumulation or depletion. The sub-basins exhibited distinct hydrological behaviour, with runoff yields ranging from 858.9 to 1,537.5 mm/year. Increasing evapotranspiration and shifts in precipitation regimes are key drivers of water balance changes, with implications for drought risk, water supply reliability, and ecosystem sustainability. By revealing these dynamics, this study highlights the value of combining remote sensing and hydrological modelling to guide climate-resilient water resource management in data-scarce regions.