Study On The Uncertain Problems Of River Water Environmental System

Based on the uncertain and incomplete characteristics of water environmental system, this thesis studies systematically problems in such areas of river water environmental system as follows: water quality assessment, water quality forecast, calculation of water environmental capacity, allocation of wastewater loads, and risk analysis of water quality exceeding a certain standard, and so on, by means of uncertain mathematics theories.The thesis begins with an introductory chapter in which the background and meaning of the research are stated, and the state-of-the-arts are reviewed. From the angle of grey relationship existing in water quality and evaluation indexes, and in evaluation indexes inside, Chapter 2 proposes a grey relation projection model for the comprehensive assessment of water quality by integrating grey system theory with the vector projection. Chapter 3 explores a forecast method for water quality. In view of the shortage of water quality information, this chapter puts forward the grey dynamic model group made up of several simple grey models to forecast the trend of river water quality, by combining the principle of the new superseding the old in grey system theory with the GM (1,1) model. Based on the deficiency of research of water environmental capacity in theory and calculation method, Chapter 4 studies the issue from the angle of the coexistence of some kinds of uncertainties, and defines the concept of blind parameters in water environmental system. On the basis of it, this chapter establishes a model with blind parameters for calculation of water environmental capacity.In order to improve the operability of allocation scheme of wastewater loads, Chapter 5 structures a multi-play evaluation index system with many quantitative and qualitative factors, which involves such fields as society, economics, environment, technology,management, and so on. In addition, Chapter 5 designs a technical route to the allocation of wastewater loads, and presents a Delphi-AHP model to determine the proportion of allocation among relative cells, by combining Satty's Analysis Hierarchy Process (AHP) with Delphi method.Chapter 6 deals with the water quality risk. Based on unascertained characteristic of water environmental system, and the thought of several uncertainties coexisting in the water environmental system, Chapter 6 defines the concept of unascertained riskof river water quality, and establishes an unascertained model to measure the risk according to the principle of blind number reliability. For the sudden risk, Chapter 6 develops an unascertained simulation model of water quality by treating parameters of the water quality model as unascertained numbers. From the river water quality model established here, not only the possible pollutant concentration intervals but also their corresponding faith degree can be obtained. According to the calculation results, the faith degree of the sudden risk can be evaluated. For the non-sudden one, the water quality risk can be assessed using the unascertained risk model provided upward, by analyizing the information of pollutant discharged and river water environmental capacity.In the end (Chapter 7), conclusions of the thesis are given.