Abstract: To quantify water supply risk caused by runoff forecast uncertainty, this paper defines water supply risk based on the probability distribution of inflow uncertainty, and develops a water supply scheduling model for the Hanjiang-to-Weihe River Basin Water Diversion Project. Multi-scale water supply risk values with different forecasting errors are obtained. The critical forecasting error of risk escalation is clarified, and the influence of inflow uncertainty on the water supply risk of this cross-basin diversion project is revealed. The results demonstrate that for water supply risk, 15% is a threshold of the runoff forecast error; the relationship between forecast error and water supply risk follows a quadratic power function. The Sanhekou reservoir can activate its multi-year water regulation to mitigate water supply risk caused by forecast errors. The water supply risks are divided into three levels: light, medium and heavy, and the thresholds for risk level upgrading are determined to be 0.117 and 0.190, corresponding to forecasting errors of 24.0% and 32.7%, respectively. The results provide a decision-making basis for ensuring the water diversion safety of the project.

Key words: inflow uncertainty, forecasting error, water supply scheduling, water supply risk, Hanjiang-to-Weihe river diversion project