A three-dimensional Budyko framework with terrestrial water storage dynamics: mechanistic modeling and diagnostic ecohydrological applications across global basins

• A new 3D Budyko framework incorporating water storage dynamics is developed. • The 3D model outperforms across diverse global basins compared to classical one. • The model performance is further enhanced when excluding anthropogenic impacts. • Water Storage Change Index serves as a novel ecohydrological stress indicator. The classical two-dimensional (2D) Budyko framework, while foundational for understanding water partitioning, faces critical limitations due to its steady-state assumption, which neglects terrestrial water storage changes (TWSC) and limits spatiotemporal adaptability. To address these limitations, this study advances a three-dimensional (3D) Budyko framework by incorporating TWSC derived from Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) datasets as a dynamic third dimension, referred to as the water storage change index (WSCI). Global evaluation across diverse basins shows the 3D framework significantly outperforms both classical and extended 2D models, especially in tropical basins where accuracy improved by 55–250 %. Using GLDAS derived TWSC (excluding anthropogenic groundwater signals) further enhances the performance of the 3D Budyko framework in human-disturbed regions like the Yellow, Indus and Tigris-Euphrates basins, confirming the climate-dominated mechanism of Budyko framework. Critically, the WSCI is proved to be a powerful diagnostic ecohydrological indicator. The deviation between the observed (GRACE-based) WSCI and the climate-driven (GLDAS) baseline provides a quantitative measure of the anthropogenic distortion of the natural water cycle. Moreover, the spatial association analysis between WSCI and Normalized Difference Vegetation Index (NDVI), using Local Indicators of Spatial Association (LISA) method, further validated its ecological relevance. It reveals distinct patterns of ecohydrological coupling across global diverse basins, including natural synergy (sufficient water availability supporting healthy vegetation), natural stress (water scarcity co-occurring with limited vegetation), and critically, human-induced unsustainability where high vegetation greenness coexists with water storage depletion. This 3D Budyko framework not only improves prediction accuracy but also offers a mechanistic tool for monitoring ecological water stress and guiding sustainable water management under climate and anthropogenic pressures.