Study On Risk Theory And Optimal Method Of Municipal Water Intake

Safety of municipal water supply depends on reliability of water intake resources and works. Carrying out optimization of water intake resources and works based on risk analysis is very significant, not only improving reliability of water supply systems, but also saving construction investment and operation cost. Municipal water intake engineering, involving in mult1-sciences and engineering such as water resource management, environmental science and water engineering, has very extensive contents. However, nowadays there is not systemic risk analysis and optimization method being used in design and operation management of the municipal water intake engineering. It is necessary to further strengthen systemic theoretical research on risk analysis and optimization of municipal water intake engineering. After reviewing references, the following aspects are thus studied in this dissertation:1. Least squares (LS) estimation of water quality model parameters is not robust in case of occurring colored noises and high-level white noises, since the random noises drift the estimated parameters away from their true values. Based on M-estimation, a robust identification method for water quality model parameters was proposed, using trust region algorithm to solve parameter estimation model. The calculation results indicated that M-estimation has strong robustness to overcome the disturbance of noises, and comparison between the LS estimation and M-estimation further demonstrated that trust region algorithm based on M-estimation possessed high accuracy, excellent performance against noises and strong robustness as well as uniform convergent, which is obviously superior to LS estimation. In case of long serial data of water quality, the data was pre-treated using wavelet de-noise. Simulation results showed that wavelet de-noise did minimize the noises disturbance and estimated noise level in which aided to determine range of M- estimation.2. Both the imperfection and fuzziness which affecting water environmental quality were analyzed according to the fuzzy and random uncertainties in the systems of water environment. A method of fuzzy-stochastic risk for water quality risk analysis in water environment was proposed based on the fuzzy probability theory. The results of calculation are consistent with the facts and uncertainties of river water quality can not be considered stochastic. The risk rate of concentrations exceeding the threshold was calculated using two kinds of definition of fuzzy safety conditions and results showed that the two definitions are the same in essence. The theory of entropy was introduced to assess the credibility of selecting the characteristic value of the membership function, and the numeric calculation on fuzzy degree of risk was carried...