ABSTRACT Quantifying and disentangling the relative contributions of climate change and intensive human activities to basin-scale mean annual runoff variations represents a fundamental challenge in hydrological attribution. This study develops an integrated diagnostic framework for the heavily regulated Xijiang River Basin, combining a SWAT hydrological model with Budyko-based water balance modeling. The methodology involves: (1) detecting abrupt changes in the mean annual runoff series and classifying impact periods; (2) applying elasticity coefficient analysis to quantitatively separate climatic and anthropogenic contributions across natural, construction, and operational phases. Results demonstrate an abrupt change in the mean annual runoff series occurred in 1992. The SWAT model performed robustly (NSE 0.77, R2 0.78 during both calibration and validation). Crucially, both methods consistently confirmed that during 2003–2017, human activities superseded climate change as the dominant driver of mean annual runoff variation, accounting for 70–80% of the observed changes. This study precisely identifies the transition point in the dominant drivers of mean annual runoff evolution, providing a scientific basis for adaptive water resource management under environmental change.
Yuan et al. (2026) studied this question.