Study On The Decision-Making Support Technology For Urban Water Environment System Control

Along with rapid urbanization and the increase of water demand, we are confronted with a series of environmental problems such as water pollution, shortage of water resource, continued decline of groundwater table and inbreak of seawater, etc. We must take efficacious measures to prevent urban water environment from worsen. Urban water environment system is provided with complex characteristic, dynamic characteristic, opening characteristic and randomicity.These complexities make the urban water environment system more difficult and complicated to control. It requires scientific means to facilitate the decision making to avoid big losses due to bad decisions.Based on the research of urban water environment control system, this paper proposed a dynamic model to support and facilitate the decision-making process and thus make the decisions more objective, scientific and practical. The main achievements of this research include:(1) Analyzed urban flood control and thus proposed a method to determine economic standards of flood control, suggested the optimal flood control strategy for a certain flood control standard .(2) Analyzed combined sewer system, proposed a simulation and optimization based method to determine interception ratio. Interception ratio is a important factor. The method proposed takes a full consideration of water quantity, water quality, point pollution source and no-point pollution source. Based on the analysis of causes of water pollution, a water pollution loss function was created.(3) By analysis of the influence of water environment capacity, this paper proposed a new method to calculate the river water environment capacity. This new method is based on continuant dynamic simulation of water flow. The method proposed uses long-term precipitation as input, calculates runoff, pollution, flow discharge, and water quality, and thus obtain the discharge hydrograph and pollutant concentration process of the cross section. It further analyzes statistically to obtain the dynamic and stochastic water environment capacity. This method combines the dynamic characteristic and stochastic characteristic of water quantity and water quality. A mathematical model of water quality rehabilitation urban lakes via periodically water renewal is proposed.(4) By analysis of the problems of current least square method, this paper proposed a least distance square method of deterministic linear correlation equation. Linear equation is widely used in data manipulation and determination of empirical formulas. Many nonlinear equations can be transformed into linear equations. Traditional least square method is obtained under the assumption that one variable is error free. But in practice, most likely both variables have errors. Thus the obtained parameters are biased and error prone. The least distance square methods consider bi-dimensional random error and are unbiased. They are more appropriate to determine linear equation parameters.