Study On Water Source Safety Evaluation Of Dahuofang Reservoir In Liaoning Province

With the rapid development of the economy, water environmental problems becomes obvious increasingly,the deteriorated water environment not only affects the life quality of of residents, but also restrictes economic development. Dahuofang reservoir is an important drinking water source in Liaoning Province, the water environment quality has been affected in recent years.In this context, it is particularly important to study the state of water environmental quality, predict water quality trends and evaluate the security situation of the water source. Which could targetedly propose water environmental protection measures, and provide theoretical basis for the security construction of water sources. The main contents and conclusions of this study are as follows.(1)After collecting the water quality monitoring data of Dahuofang reservoir,establish the water quality evaluation models based on fuzzy comprehensive evaluation, based on BP neural network, based on the evaluation model of gray correlation analysis and based on principal component analysis, which are based on Surface Water Quality Standards (GB3838-2002), water quality grade is divided into five grades.After comparing and analyzing the results of the four methods,it concludes that the results of BP neural network evaluation method and principal component analysis are basically the same,the results of fuzzy comprehensive evaluation method are close to them, the evaluation results are slightly lower, the results of grey the evaluation method are different from other three methods greatly, for reference only. The evaluation results show that the Hun River is the most polluted in the input rivers, evaluated as grade HI or IV,She river and Suzi river also have a degree of pollution, the main pollution source is nitrogen, produced by non-point sources of chemical fertilizers, pesticides, sewage etc.. Water quality in the reservoir area is good,but which also has a high total nitrogen content.(2)Establish two different water quality prediction model using BP neural network forecasting method and gray theory prediction method, BP neural network prediction method selected indicators of water pollution monitoring data of other six sections except outbound mouth in Fushun section from 2005 to 2011 as the input samples to establish a network,data of outbound mouth in Fushun section is use as the output layer neurons,simulate and train the network. Data of 2012 is used to verify the network.. After training the network, accuracy is satisfactory, the relative error is between 0.775%-9.07%. Gray prediction theory is changing raw irregular data adopted of certain treatment to regular time series data,and then establish the differential expression model. The accuracy of water quality prediction model of each section reached 90%.(3) Defines the concept of water sources safety. According to the theory of sustainable development, based on the water sources’ security composition of Dahuofang reservoir, build a three-layer index system, including target layer, criterion layer and index layer.Target layer is for safty level of water source, criterion layer contains six sucurity aspects including water quality,wanter quantity,ecology, engineering, control system and management system. index layer involves 20 indexes following the criterion layer. Reference to domestic and foreign scholars study and combine with its own environmental conditions of Dahuofang reservoir water source,and then formulate grading standards of the indexes,and divide each index into Ⅰ (very high), Ⅱ (high),Ⅲ (middle),Ⅳ (low),Ⅴ (very low) five grades corresponding to the safety level of water source.(4) Index weight is determined by the Analytic Hierarchy Process, safety level of each index is indicated by membership degree,and which is determined by the method of combination of qualitative and quantitative. Finally, calculate the safety level of each criterion layer and the overall water source through comprehensive evaluation method. Engineering security is "very high" level,water-quality security is "high" level, water-quantity security and management system are "medium" level, ecological safety and control system are "low" level. The overall safety level of water sources is etween "high" and "medium",close to upper-middle level of safety.