An MILP based optimization model for reservoir flood control operation considering spillway gate scheduling

Abstract

Reservoir flood control operation is an important and effective measure for avoiding or reducing flood disasters. Considering that reservoir operation is a control process that essentially manages the spillway gates to increase or decrease the amount of released water, this paper focuses on studying the reservoir flood control operation which considers spillway gate scheduling. Minimizing the peak outflow from the reservoir is adopted as the optimization objective to protect downstream areas from flood disasters. In addition to the conventional reservoir constraints, the operation constraints of individual spillway gates and the influence of the reservoir forebay water level and opening degree on the gates’ discharge capacity are also well considered to obtain precise scheduling. The nonlinear factors, especially the objective function in the form of maximin, the three-dimensional water discharge curves, and the rules for the opening and closing sequence of the spillway gates, are linearized through several strategies. The original nonlinear and non-convex model is then converted into a standard mixed-integer linear programming (MILP) formulation. The results for the real-world case study indicate that: 1) the proposed model is believed to be computationally efficient with a calculation time of about 30 min; 2) for the flood events with return periods of 10 years and 100 years, the flood peaks are reduced from 4160 m3/s to 3681 m3/s and from 11007 m3/s to 9293 m3/s, representing decreases of 11.5 % and 15.6 %, respectively. The outflow curves become more stable, demonstrating that the flood control pressure on the downstream had been relieved after optimization; 3) the proposed model can produce more realistic and executable flood control operation scheduling compared with the conventional optimization model without considering spillway gate scheduling. These research findings can provide an effective reference for both the operators of reservoirs and researchers in the field of reservoir flood control operation.