Abstract: The influence of cascade hydropower stations on the runoff and flood process of Yingluoxia hydrological station at the outlet of Heihe River is analyzed by using the double cumulative curve method, MK test method and Gini coefficient method based on the monthly annual runoff, annual maximum peak discharge, flood process of Yingluoxia hydrological station and precipitation in the upper reaches of the Heihe River.Results demonstrate that the construction and operation of cascade hydropower stations in the upper reaches of Heihe River has no large impact on the change of annual runoff, but has a certain impact on the annual distribution of runoff and flood process.After the joint dispatching and operation of the power stations, the regulation and storage of the reservoir in front of the dam has changed the natural runoff process and has a significant impact on the annual distribution of runoff.The annual distribution uniformity showed a transition in 2001 and a significant increasing trend from 2017 to 2020.The artificial rising and lowering of the gate resulted in the straight rising and falling of water level, the elongation of flood process, the expansion of peak flood in the form of steep rise and fall, and the increment of the rise and fall rate and change frequency.The research findings offer theoretical basis for strengthening the scientific operation of hydropower stations, the construction of water ecological civilization and the sustainable development and utilization of hydropower and water resources.

Key words: runoff, MK test method, Gini coefficient, flood process, cascade hydropower station