A Multi-objective Decision Making Model of Reservoir Operation Considering Balanced Feasibility in Both the Past and Future and its Application to Three Gorges Reservoir

Climate change poses significant challenges to water resources management. At present, an increasing number of studies on water resources management, especially reservoir operation, consider the uncertainty of climate change in the design of management strategies in order to mitigate its negative impact. Existing multi-objective decision making (MODM) approaches which consider the uncertainty of climate change, either solely provide the satisfying scheme on the basis of evaluation results adapting to limited future climate change scenarios or have complex and theoretical implementation steps and ignore the interrelationships of many optimization objectives. Motivated by the emerging need for an optimum decision-making scheme with long-term and sustainable applicability in the practice of reservoir management, this paper aims to develop a multi-objective decision-making model of reservoir operation considering balanced feasibility in both the past and future. It consists of the following four modules: (1) the multi-objective optimization model of reservoir operation is built based on historical streamflow and then solved by the evolutionary multi-objective direct policy search (EMOPDS) with non-dominated sorting genetic algorithm-II (NSGA-II); (2) the evaluation criteria matrix is defined in view of future sustainable applicability, and visual analytics is used to qualitatively describe the objective interrelationship and interrelationship propagation from the past to the future; (3) the structural equation model (SEM) is introduced to quantify objective interrelationships; and (4) the objective-based space coordinate system (SCS) is established, and the concept of the spatial distance is adopted in order to derive evaluation criteria weights based on the quantitative coefficients of the SEM. Finally, the optimum scheme is determined by the incorporation of evaluation criteria and their weights. The Three Gorges Reservoir (TGR) is selected as a case study, which simultaneously undertakes hydropower generation (pow), ecology (eco), and water storage (stor). Results indicate that eco negatively interacts with both pow (-0.83) and stor (-0.92); however, pow is positively correlated with stor (0.97). More importantly, although SCS-MODM, FOS-1, and FOS-2 outperform in stor, pow, and eco, respectively, SCS-MODM has more robustness in both benefit and operation process than FOS-1 and FOS-2. Therefore, SCS-MODM facilitates decision makers to make a sustainable and balanced decision for the management of water resources system under uncertain climate change.