Abstract:Water resources are strategic resources that affect the high-quality development of the Yellow River Basin. Under the influence of human activities and climate, the runoff in the upper and middle reaches of the Yellow River has undergone changes greatly. Therefore, the variation characteristics of the runoff in the Yellow River and their prediction have great importance on the rational development, allocation and regulation of water resources. This study used the runoff data measured from 1950 to 2018 at the Tongguan station of the Yellow River to analyze the characteristics of runoff changes in the upper and middle reaches of the Yellow River by M-K and other methods. The change trends of runoff at different frequencies in the next 20 years were also predicted. The results showed that the runoff in the upper and middle reaches of the Yellow River decreased significantly from 1950 to 2018; the runoff changing point of the Tongguan station of the Yellow River was located in 1985, and the decreasing trend was significantly higher than before; through the optimized GM (1,1) model, 5% and 95% frequency runoff predictions indicated that the runoff change in the next 20 years would be 113.38 to 210.35 billion m3, and it would continue to decrease and stabilize; this optimized model had good simulation results for the Tongguan hydrological data of the Yellow River and was suitable for frequency optimized prediction of long sequences of low decreasing hydrology.