The Research Of Water Environment Assessment In Environmental Protection Dredging Engineering

Environmental protection dredging is one of the main ways to control the intrinsic pollution of lake, it mainly around precise dredging, sediment disturbance, pollutant diffusion, secondary contamination and the disposal of dredged soil. Creating the situation for restoration of aquatic ecosystem ,coordinating with water environment comprehensive treatment plan and finally achieve the goal of improving the quality of water environment at the same time of cleaning the polluted sludge is the purpose of environmental protection dredging. But the theory and practice about environmental protection dredging are weak, and there is still no qualitative analysis about water equality in lake and reservoir.Water environment assessment is a basic important work for water resource protecting. Water environment assessment can be classified into water pollution assessment, eutrophication assessment, sediment assessment and hydro-ecosystem assessment by assessing object. It can also be classified into single-factor method, multi-factor method and others. The single-factor method is not accord with the inner oneness of water environment. So, a great deal of research has been done on multi-factor method. In this paper a grey fuzzy comprehensive evaluation method based on fuzzy theory for water quality assessment is developed.The multi-grade cascade grey fuzzy comprehensive evaluation method was presented based on the analysis of present water quality. The key of this method is fuzzy comprehensive evaluation method. Combined with cascade theory, the great amount of complicated phenomena in water quality assessment and the relations between different factors were qualified. Then, the grade of water quality was gained. When analyzing and applying the data, the weight of each factor was determined by principal component analysis method which is based on the measured data of sample. This method avoided the subjective differences of expert analysis weight assignment method. Meanwhile, the results from fuzzy comprehensive evaluation were analyzed by weighted average method. This avoided information loss when using maximum subordination principle.In the case study of Shiyan Reservoir in Shenzhen, the water quality and eutrophication status were assessed using the multi-grade cascade grey fuzzy comprehensive evaluation method presented in this paper. The practicability was validated in this case.