Study On Water Environment Quality Evaluation Based On Cloud Model

China is a water shortage country.The per capita freshwater resources is only 1/4 of the world average,and water resources distribution is extremely uneven.China is one of the 13 countries which has the poorest per capita water resources in the world.Ningxia is one of the six provinces(regions)with severe water shortage in our country,the characteristics of its water resources can be summed up as a small quantity and poor quality.In recent years.Ningxia water shortage in resources does not solve the problem situation,due to pollution caused by water shortage have become increasingly prominent.Now the Ningxia people's health and social economic development has been seriously affected by the quality problems of water environment.The Yellow River is the main source of Ningxia surface water,so the water environmental quality assessment of the Yellow River is helpful for us to understand and grasp the water pollution,water quality status and the trend of Ningxia,for the rational use of water resources and water environment protection to provide a scientific theoretical basis.The water environment system is a complex system with many layers and many uncertainties.The traditional methods of water quality evaluation are generally one-sided and unreasonable.Therefore,this study attempts to use a new method of water quality evaluation in the comprehensive evaluation of water quality in the mainstream of the Yellow River.Compared with other water quality evaluation methods,the advantages and disadvantages of cloud model in the comprehensive evaluation of water environment quality are studied.Based on the investigation of water quantity,water quality and pollution sources of the Yellow River,We use the actual monitoring and pollution characteristics of 6 state-controlled or provincial control sections in the Yellow River in 2012.The comprehensive evaluation of water quality in the Yellow River is carried out by the comprehensive evaluation method of entropy weighted cloud model,based on 7 indicators of the dissolved oxygen(DO),potassium permanganate index,chemical oxygen demand(COD),five day biochemical oxygen demand(BOD5),ammonia nitrogen,total phosphorus and fluoride.The evaluation results are compared with the results of single factor evaluation and matter-element method.The results show that:In the comprehensive evaluation of water quality,the single factor evaluation method is too one-sided and pessimistic,the credibility and objectivity of the results are lower than the other two methods.Matter element analysis method in the practical application of the process is cumbersome,large amount of calculation,resulting in the possibility of error in the evaluation results are large,so the matter element analysis method in the comprehensive evaluation of water quality is slightly worse.By comparing the theory and process,entropy cloud model comprehensive evaluation method not only is better than the single factor evaluation method and matter element analysis method in theory,and in practice to evaluate the water quality,the more operational,more accuracy.At the same time,by comparing the 24 water quality evaluation results obtained by the comprehensive evaluation method of matter element analysis and entropy weighted cloud model,the 17 water quality evaluation results are the same,and the other water quality evaluation results are very close.Combined with the actual situation of field investigation,that the entropy cloud model comprehensive evaluation method is applied in the comprehensive evaluation of water quality of the Yellow River in Ningxia section,and compared with the single factor evaluation method and matter element analysis method,the comprehensive evaluation of water quality results are more accurate,comprehensive and objective.Based on comparing and analyzing the results of comprehensive evaluation of water quality in the Yellow River,the water quality of the 6 sections of the Yellow River main stream in the current year has not changed greatly,and the water quality is better.In space,the upper reaches of the Yellow River water quality is better than the downstream water quality.In time,the best water quality during the period of water,wet and dry season water quality is close to,slightly less than the water level.At the same time according to the present situation of water quality of the Yellow River in Ningxia province of the analysis and investigation of pollution sources,primarily that the influence of water into the yellow water on the Yellow River water quality plays an important role,therefore,from the source to control the concentration of pollutants,which can effectively reduce the risk of water pollution.