Risk-based multi-objective optimization model for the inter-basin water diversion system under multiple uncertainties and water-use constraints

Inter-basin water diversion has emerged as a critical measure for achieving a balanced distribution of water resources across basins. This process requires careful planning and implementation of an effective water supply operation scheme. However, an observed decrease in prediction accuracy with extended time periods reduces the effectiveness of long-term water resource management, presenting a dilemma between the risk of water scarcity due to insufficient water diversion and water wastage resulting from excessive diversion. Moreover, stringent regulations on water resources management are critical to achieving intensive water use. Setting limits on the dynamic spatial-temporal allocation of water resources poses a persistent scientific issue requiring immediate attention. Therefore, this study proposed a multi-objective risk-based optimization model for the inter-basin water diversion system under multiple uncertainties and water-use constraints. Backed by probabilistic predictions of local streamflow and water demand via scenario tree method, the water shortages and wastage risks along with costs associated with water diversion were identified. Simultaneously, a dynamic decomposition method for the total water-use constraints, considering changes in various streamflow scenarios, was proposed. Real-time water supply operations under severe constraints and heightened uncertainty were investigated in this study, while the eastern route of the South-to-North Water Diversion Project in Jiangsu Province, China was selected as the case study. The principal findings were as follows: (a) Conflicting relationships exists in this complex system, with the loss of water shortage and the cost of water diversion being the main contradictions. By utilizing high-prediction information, the water diversion was reduced by 41.9%, spilled water by 72.0%, and the water deficit by 10.6%, contributing to achieving an equilibrium in terms of cost, loss, and risk of water diversion and provision; (b) The total water-use constraint effectively controlled inter-basin water diversion and spillage, thus promoting the optimal exploitation of local water supply potential. The core of the water-use constraint is to promote the utilization of water resources through the compression of inter-basin water diversion; (c) By applying the dynamic decomposition of total water-use constraint, the water supply and consumption in a typical dry year increased by 15.46 × 10⁸ m³, theoretically reducing the water deficit by 18.0% compared to the rigid constraint condition, meeting essential agricultural needs during severe drought conditions; (d) The incorporation of chance-constraint functions allowed for a more aggressive water diversion strategy (increasing additional water diversion by 0.574 × 10⁸ m³) while mitigating risks associated with operational decision-making, thereby enhancing reliable water resources management.