Research And Application Of Surface Water Quality Comprehensive Evaluation Method

Water resources are fundamental resources for maintaining social and economic development and ecological balance.With the rapid development of industrialization and urbanization,the problem of non-point source pollution of surface water in river basins is becoming increasingly prominent.Water quality evaluation is a fundamental task in ensuring water environment management.Regular and accurate evaluation of water quality based on various indicators in the water can timely understand abnormal conditions of surface water,which is of great significance for water pollution control and the use of water resources.This thesis takes Mulan River Basin and Hagilu River Basin in Putian City,Fujian Province as the study area,collects water quality sample data of 10 sections from 2018 to 2020,selects dissolved oxygen,total phosphorus,five-day biochemical oxygen demand,permanganate index,and ammonia nitrogen as five indicators for water quality evaluation,and builds a comprehensive evaluation model for surface water quality of the basin on this basis,and designs and develops a corresponding management system for water quality evaluation of the basin.Firstly,based on the "Environmental Quality Standards for Surface Water"(GB3838-2002),analysis and research were conducted on the water quality of sections in the Mulan River Basin and Qilu River Basin.Three typical water quality evaluation methods,namely water quality comprehensive index method,fuzzy comprehensive evaluation method,and fuzzy clustering method,were selected to comprehensively evaluate the water quality of each section.Secondly,a water quality comprehensive evaluation model coupled with swarm intelligence optimization algorithm and projection pursuit technology was constructed.The optimal projection direction of the projection pursuit model is optimized using the social spider optimization algorithm,moth swarm algorithm,and whale optimization algorithm,respectively,in order to achieve graded evaluation of water quality.Then,based on the water quality evaluation results,three algorithms were compared.The experimental results showed that the optimization ability and convergence stability of the social spider optimization algorithm were slightly better than those of the moth swarm algorithm and the whale optimization algorithm.Then,based on the evaluation results of four water quality evaluation models for each section,a comparative analysis is conducted on the water quality grades in the time and spatial dimensions of each section.On this basis,the characteristics and applicable conditions of different water quality comprehensive evaluation models are summarized.Finally,based on the various water quality comprehensive evaluation models constructed,a water quality comprehensive evaluation management system for the river basin is designed and implemented.The system can comprehensively evaluate the water quality of different sections by selecting different water quality evaluation models,assist the staff in the management,utilization and decision-making of water resources,and realize the sharing and integration of water resources information.