Determining the risk-moderate criterion for flood utilization

Flood utilization can alleviate the shortage in water resources in North China. As an important part of flood utilization criteria, the risk-moderate criterion ensures reasonable and safe exploitation of water resources. For the adjustment of flood limit water levels (FLWL), an analysis method is proposed, which determines risk-moderate criterion by computing flood regulation with the designed floods of different return periods and modeling long-time series water supply with reservoir scheduling model. This method is applied to Miyun Reservoir in Beijing. Results show that the uplift of the major-flood-period FLWL from the initial value of 147.00 m to the current value of 152.00 m is relatively reliable, and its upper threshold can be 153.20 m further. The upper threshold of later-flood-period FLWL for reliable flood utilization is 155.40 m, compared with 154.00 m at present. The water supply assurance rates increase by 0.3% and 0.01% in these two cases, respectively; and the risk rates of the dam and downstream flood control areas are kept within 0.01% and 1%, respectively. These risk rates satisfy the designed standard and risk-moderate criteria of flood utilization.