Multi-decadal validation of the Budyko framework in mainland China: A watershed-climate-geographic zoning approach

Study region Mainland China, covering diverse hydroclimatic and physiographic regions, during 1980–2022. Study focus This study evaluated the applicability of the Budyko-Fu framework across mainland China using three regionalization schemes: watershed boundaries, climatic zones, and geographical regions. The analysis examined spatial heterogeneity in model performance and in the Budyko parameter ω, and compared how different zoning approaches affect large-scale Budyko assessment in a geographically complex setting. New hydrological insights for the region The Budyko framework showed moderate applicability across mainland China, with pronounced regional heterogeneity. Watershed-based regionalization performed best overall (R² = 0.45), whereas climate-based zoning performed best after excluding predefined impacted areas (R² = 0.69). Poorer model performance was concentrated in regions affected by glacier melt, strong climatic heterogeneity, and intensive human disturbance, indicating that large-scale Budyko assessment in mainland China depends strongly on the match between regionalization units and hydroclimatic controls. The proposed identify-exclude-optimize strategy provides methodological guidance for applying the Budyko framework in other spatially heterogeneous regions.