Evaluation of multi-objective optimal allocation schemes for water resources in hilly regions based on improved cloud model

Abstract

[Objective] The undulating terrain and uneven spatiotemporal distribution of rainfall in hilly regions result in rapid runoff generation and concentration, making it difficult to effectively collect water resources. This leads to issues such as frequent flooding in lowlands and droughts in uplands. Therefore, a coordinated water allocation and supply system for hilly regions is required to alleviate the conflict between water supply and demand. [Methods] Based on the integrated water supply approach in hilly regions, a multi-objective optimal allocation model for water resources in hilly regions was established. The Non-dominated Sorting Genetic Algorithm-Ⅱ(NSGA-Ⅱ) was improved in three aspects: crossover, mutation, and sorting processes within the same non-dominated layer, for solving the model. A comprehensive evaluation indicator system for water resources was developed. The cloud model was improved using the Analytic Hierarchy Process(AHP) for evaluating the set of schemes and selecting the overall best multi-objective optimal allocation scheme for water resources. Finally, the theoretical method was applied to the Liuhe District, Nanjing City, to conduct a case study. [Results] (1) The improved NSGA-Ⅱ algorithm was employed to obtain the Pareto solution sets for Liuhe District in 2025 and 2035. These sets were screened based on economic,social, ecological benefits, along with optimal coordination, resultsing in seven allocation scheme sets for each year.(2) After the seven scheme sets for 2025 and 2035 were evaluated using the cloud model rating, the optimal scheme set for both 2025 and 2035 was scheme 4, representing the optimal coordination between economic and social benefits. The scores were 89. 87 and 90. 95, respectively. [Conclusion] A multi-objective optimal allocation model for water resources in hilly regions is established.By improving the traditional NSGA-Ⅱ algorithm in three aspects, the quality and rationality of the solution sets are significantly enhanced. A multi-level evaluation indicator system is established. An improved cloud model is innovatively applied to quantitatively evaluate the schemes, and the optimal scheme is selected through comparison. This approach provides a complete technical pathway of “model construction-algorithm optimization-scheme comparison and selection” for efficient water resource allocation in hilly regions. It can provide a reference for decision-makers, alleviate water supply-demand conflict, and promote comprehensive and coordinated development in hilly regions.

Keywords

hilly regions / optimal allocation of water resources / improved NSGA-Ⅱ algorithm / scheme evaluation / improved cloud model / multi-objective optimization / Pareto optimal solution / Analytic Hierarchy Process(AHP)