Runoff on the Chinese Loess Plateau has declined substantially over recent decades, but the relative roles of climate change and non-climatic disturbance remain debated. Here, we provide a robust regional attribution of runoff reduction across 14 major catchments during 1961–2009 by integrating seven Budyko-based climate elasticity methods with long-term hydro-meteorological analysis and change-point detection. Across the region, runoff and runoff coefficients decreased markedly, while evapotranspiration and leaf area index increased, indicating a widespread reduction in catchment water yield. Runoff showed consistently greater sensitivity to precipitation than to potential evapotranspiration, highlighting precipitation as the primary climatic control on runoff variability. However, the Budyko-based climatic component explained only part of the observed runoff decline, and the residual component not explained by annual precipitation and potential evapotranspiration was large in many catchments, with estimated contributions generally exceeding 50% and reaching more than 80% in several basins. Independent evidence, including vegetation greening, the expansion of ecological engineering measures, and increasing anthropogenic water demand, suggests that this residual was at least partly associated with human disturbance, although other non-Budyko climatic and hydrological processes may also contribute. These results indicate that annual precipitation and potential evapotranspiration alone cannot explain runoff decline across much of the Loess Plateau and underscore the need to jointly consider climatic forcing, land surface alteration, and direct human water use in regional water management.
Yang et al. (Thu,) studied this question.