Research Of Uncertainty Theory And Methodology In Water Environment--A Case Study Of Three-Gorge Reservior

This paper introduced from the research evolutions of uncertainty theory and methodolodgy, which was applied to water environmental system. Then it was presented that if uncertainty theory and methodolodgy was instructed to found model of environmental system, uncertain objective discipline could be recognized in essence. In this paper, a case study was exampled by Three-Gorge Reservior, which was famous at home and abroad. And uncertainty theory and methodolodgy was applied to predict water quality of the Reservior. And we hope to found a model which is more accorded with objective facts and enhanced practicability.For a long time, river water quality prediction and assessment was always an important research task, which had many theory bases and successful applications, but they were all confined to ideal determinate water quality model and uncertainties of complex river system were seldom considered. Now based on past studied results and considering uncertain characteristics of Three-Gorge Reservior, such as watercourse shapes, hydrologic characteristics and pollutant discharge, this paper created two-dimensional water quality prediction model based on finite-element method. Then Monte Carlo method was applied to calculating water quality probability distribution after Three-Gorge Reservior's impoundment, which provided more information for water quality management of Three-Gorge Reservior.Main research contents were indicated as follows: (1) two-dimensional stochastic model formation process and stochastic parameters were introduced. Then integrated shannon entropy with numerical algorithm of finite-element method, quantitative optimization model of grid width was indicated. And optimization validity was justified to enhance model's application and reliability by sensitivity analysis; (2) considering the uncertainty factors of population, economic development, industrial and agricultural structure regulation, environmental protection policies and pollution treatment, etc, pollutant discharge amounts in 2010 were predicted as three aspects of high pollution load, middle pollution load and low pollution load; (3) three hydrologic flows ( including 7Q10 designed period, low water period and flood period) were determined. To realize how different flows affected water quality, three hydrologic flows were integrated with three pollution loads; (4) in this paper, CODcr, BOD5, NH3-N and TP were regarded as water quality indexes, and based on differentpollution amounts and hydrologic flows, nine schemes were designed and Montle Carlo method was applied to statistical calculation; (5) four cities of Chongqing, Changshou, Fuling and Wanzhou were made examples to simulate bank pollution strap after impoundment; (6) to be aware of water categories of different sections, fuzzy theory and probability theory were used to assess 20 important sections; (7) according to results of bank pollution strap, some treatment measures were preliminarily presented about point pollution and non-point pollution of Three-Gorge Rerservior.Thus, some research merits were summarized as follows. (1) when pollutant's shannon entropy was most maximal in unit cell, pollution distribution would become even and its grid width was optimized at this time. So this paper proposed optimization grid width theory based on shannon entropy, which provided bases for determination of grid width and division of flow zones and optimizd water quality model; (2) Monte Carlo method was used to collect data and analyze statistical results of probility distribution, which enhanced reliability of results; (3) The assessment method of fuzzy theory and probability theory made results more close to objective facts, which made up deficiency of subjective judgement; (4) in this paper, Matlab language was applied to the treatment of data and matrix. And excellent integration between computer programme and mathematical model enhanced reliability and practicality of the model.Because a lot of uncertainties were objectively existed in water environmental system, if we want to r...