Joint optimal operation of the South-to-North Water Diversion Project considering the evenness of water deficit

Abstract. Inter-basin water transfer project is the main measure to address the water deficit crisis caused by uneven distribution of water resources. The current water transfer operation mainly tends to be in areas with small water transfer costs and is prone to encounter the problem spatial and temporal imbalances in water allocation. To address the aforementioned issues, this paper defines a Water Deficit Evenness Index (WDEI) aimed at minimizing the regional differences in water scarcity and sharing the pressure of water scarcity as a social demand objective. This index is incorporated into a joint optimization model for the South-to-North Water Diversion project (J-SNWDP) in Jiangsu, which comprises both the ecological objective of the total water deficit (TWD) and the economic objective of the pumping water (PW). Further, the NSGA-III algorithm and multi-attribute decision-making were applied to solve the model and obtain an optimal operation strategy. The results showed that: 1) The WDEI defined in this paper can mitigate the synchronized water scarcity in certain water users. In typical normal years (wet year and dry year), the Water Deficit Evenness Index shows a reduction of 94.2 % (81.8 %, 76.7 %) compared to the historical operation strategy; 2) The optimized operation strategy can significantly reduce TWD and PW by 82.06 % (37.69 %, 52.36 %) and 45.13 % (3.25 %, 21.51 %) compared with the historical values, respectively, which can improve the water supply satisfaction and reduce the project cost. At the same time, the lake storage capacity of the optimal operation strategy performs well, and the water transfer efficiency of the river is significantly improved. 3) In this paper, targeted optimal operation strategies and potential ways to secure the project tasks are proposed for different natural flow. Overall, it is of great significance to study the water supply equity in the Jiangsu section of the South-to-North Water Diversion Project to alleviate the concentrated water deficit in Jiangsu Province and other similar regions.