Research Of Regional Surface Water Environment Quality Evaluation

Regional surface water environmental quality assessment is an important part of Hydrology and Water Resources, and it is the basic work of planning, development, utilization, protection and management of water resource.It provides the decision-making of water resources and water environment for national economic and social development.This paper relates to the application status, problems and insufficiency of regional surface water quality evaluation method in domestic and foreign. It has a comprehensive analysis of the technical framework of water environmental quality assessment, and it is discussed that the application of the quality assessment methods based on complex theory, It mainly includes the following content.(1)It is summarized that strategy, methods, and procedures of the regional surface water quality evaluation, in terms of evaluation standard, the selection of evaluation factors, weight determination, representative value selection and the method etc. And the scientific theoretical system of the comprehensive assessment is proposed.(2) On the basis of the comprehensive consideration of water quality evaluation model, and the analysis of the different evaluation method and its advantages and disadvantages. The improved TOPSIS method and matter-element evaluation model are selected, the principle and construction process of the two comprehensive evaluation models are described. And then the models are applied on evaluating the water quality of the Chongqing section of the three Gorges Reservoir to demonstrate its feasibility and applicability. It is intimated that the different methods of comparative analysis has coherence to results,except the grade of water quality of some monitoring sections is lower by the method of matter-element evaluation model than the improved TOPSIS. And it is showed that the water quality in the mainstream of the survey region is worse, and the grade of most of the water quality monitoring sections is exceedⅢ,but the water quality in the tributary river section is generally in good condition ,and reach the management goal of water quality.(3) The variation trend of water quality and its influence factors were analyzed. The water quality is generally worse in the high-water period than in the drought period and the level period, and the density variation trend of the selected water quality indexes in three water period primary showed a decreasing trend. It is analysed on water quality trend of the concentrations of Total Phosphorus,Permanganate Index and oil type in the survey region using the method of seasonal Kendall test. The result shows that the concentrations trend primary showed a decreasing change, indicting that the water quality of the Three Gorges Reservoir was getting better in general during the past six years.