The Research Of Water Pollution Issue Based On Robust Decision Making

With the rapid development of human society and economy,the contradiction between economic development and lake pollution has been aggravating gradually.A lot of manpower,material and financial resources have been put into the lake management issues,which did not make the problem of lake pollution greatly improved,so it is obviously important to do more research on the water pollution control.In this context,this paper analyzes the problem of lake pollution from the perspective of system science.As the complexity of the lake that is a typical composite system makes the lake complex system show great random,ambiguous and uncertain,etc.,it is necessary to take into account the deep uncertainty of the lake composite system in the study.Therefore,this paper introduces the relevant theory of robust decision making,and takes the pollution problem in Taihu Lake as an example to make robust decision.First of all,this paper systematically reviews the theory of deep uncertainty and robust decision making(RDM),and compares the difference between traditional decision and robust decision making.After the basic theory of robust decision-making is integrated and refined,this paper forms a detailed analysis methodology of robust decision making which consists of problem formulation,uncertainty analysis,scenario discovery,finding out the strategies which need to be traded off and tradeoff analysis,which can be applied to analyze the single and many objective evaluation problem.In addition,this paper analyzes the pollution problem in the lake basin from the perspective of compound system.Then,based on the building methodology of DICE model,this paper establishes the model of pollution problem in the lake basin,which is composed of objective function,economic model and environmental model.In the model construction process,this paper takes the pollution problem in Taihu Lake as an example to build the model,which is integrated by three parts:objective function,economic model and environmental model.The objective function is to optimize the social welfare function from 2015 to 2040 under different governmental strategy.The economic model consists of the Cobb-Douglas production function,pollution loss function,pollution abatement cost function,capital accumulation equation and other functions.The environmental model comprises the water quality model and the model of nitrogen emission into the Taihu Lake in rural,industrial,and urban areas.Then,many parameters in the objective function,the economic model and the environmental model are estimated based on the relevant statistical yearbook and data.At the same time,this paper summarizes 12 deep uncertainty parameters in the the economic system,natural systems and governance strategies.In the process of robust decision making,the dissertation firstly put forward 5 strategies based on pollution abatement documents of Taihu Lake published by goverments at all level,which is letting things drift(doing nothing),cutting down 36%the emission of nitrogen every 5 years,cutting down 16%the emission of nitrogen every 5 years,invest pollution controlling budget approximately 0.69%of GDP in Taihu Lake Basin,and keeping the amount of nitrogen concentration in Taihu Lake under 2 mg/L respectively.After sampling the deep uncertainty parameters by Latin hypercube sampling method,20000 scenarios are generated.In the uncertainty analysis process,it is found that most of the upper quartile of the relative regret value of the third strategy,cutting down 16%the emission of nitrogen every 5 years,is lower,so the third strategy is regarded as an initial robust strategy.In the scenario discovery process,patient rule induction method are applied to identify the vulnerability of the initial robust strategy and create vulnerable scenario that if the third strategy is taken when rural nitrogen emission is high,industrial and rural pollution abatement cost is higher and the self-purification abilities of Taihu Lake is low,it will be strong possible that the nitrogen concentration in Taihu Lake is higher than 2mg/L.In the strategy robustness analysis process,after analysis on vulnerable scenario and non-vulnerable scenarios,it is found that the third strategy is more robust than the other.Furthermore,it is also found that four of the 12 deep uncertainty parameters are the key factors,which is the decrease coefficient of rural nitrogen emission intensity,retention coefficient in Taihu Lake and the coefficient the of industrial and rural pollution abatement costs.Moreover,with the prolongation of the strategy implementation,the decision makers need to pay more attention to the two of these four key uncertain parameters,which is the decrease coefficient of rural nitrogen emission intensity and the coefficient the of rural pollution abatement costs.Finally,the robust strategy is selected and the complexity of the problem is reduced by using the method of robust decision-making,and dimension,which help the decision-maker to identify the more critical influencing factors and make decision.