Comprehensive Benefit Assessment of the Middle Route of South-to-North Water Diversion Project Based on Markowitz Theory

In the context of global climate change and the water-carbon peak target, improving water security in arid regions is a persistent challenge in global water resources management. Water diversion projects can serve as an important measure to effectively alleviate the uneven distribution of water resources, achieve rational allocation and efficient utilization of water resources. However, how to achieve the maximization of comprehensive benefits during the process of water allocation is also an urgent problem that needs to be solved. This study focuses on the Middle Route Project of the South to North Water Diversion Project in China, selecting four important municipalities and provinces during 2015 to 2021, namely Beijing, Tianjin, Hebei Province, and Henan Province, based on the actual benefits of the water receiving areas of the middle line project. Nine representative indicators related to social, economic, and ecological benefits were selected to evaluate the optimal combination of water resource allocation in the water receiving areas along the central line, in order to achieve the maximum comprehensive benefits and solve the problems of high water safety guarantee requirements and difficult balanced water distribution in urban agglomerations in the water receiving areas. Through the calculation of the Markovsky theoretical model, the results show that when 79.9% of the water conveyance is used to generate social benefits, 15.8% of the water conveyance is used to generate ecological benefits, and 4.5% of the water conveyance is used to generate economic benefits, the project achieves the maximum comprehensive benefits. This computational model method can be used to provide technical support and scientific reference for the optimal allocation of water resources in cross regional water transfer projects.