Stream flow plays a crucial role in environmental, social and economic contexts. It is of significance to investigate the causes of change in runoff for better water resources management. This study detects the variation trend of recorded runoff of the Gushan River, a tributary of the Yellow River located on the Loess Plateau with severe soil and water losing, and investigates the impacts of climate change and human activities on runoff using hydrological simulation approach. Results show that the recorded runoff at Gaoshiya station on the Gushan River has experienced a significant declining trend from 1954–2013 with an abrupt change occurring in 1973. SimHyd rainfall runoff model performs well for monthly discharge simulation with Nash–Sutcliffe coefficient of 82.6 % and relative error of 0.32 %. Runoff depth over the catchment in 1980–2013 reduced by 52.4 mm compared to the previous period, in which human activities and climate change contribute 61.5 and 38.5 % of the total runoff reduction, respectively. However, the human-induced impact tends to increase. Therefore, efforts to improve the ecology of the Loess Plateau should give sufficient attention to the impacts of human activity.
