Study On Water Environmental System Safety Management Of The Water Supply Control Project

Studying on the water quantity and quality evolution laws and assessing water environment system risk of the water supply projects and therefore making out countermeasures, have important significance for the water supply security in northern cities of China. Taking Yuqiao Reservior as the research object, the water environment system risk of Yuqiao Reservoir was analyzed and evaluated in this dissertation. And based on the risk analysis result, a set of technical measures was put forward to cope with the Yuqiao Reservoir's potential pollution risks. The main contents and achievements in this dissertation can be summarized as following:(1) Taking the annual rainfall series and annual runoff series as research objects, such methods as Markov theory, runs theory, S-transform, accumulated difference curve and linear sliding average were comprehensively applied to study on the wetness-dryness persistence laws, wetness-dryness changing laws, multi-time scale fluctuation features, periodic variation features and changing trends of hydrological time series in the Yuqiao Reservoir watershed.(2) Modeling procedure of multivariate joint distribution based on Copula theory was detailly discussed and illustrated in this dissertation. And then, the wetness-dryness compensation characteristics of different water source regions of the Yuqiao Reservoir were quantitatively analyzed by means of multivariate joint distribution model.(3) The 3-dimensional display technique was applied to illustrate the statistical analysis results of water quality status of the Yuqiao Reservoir watershed in the past 23 years. Standard-exceeding multiple and frequency was plotted on the coordinate system of which x-axis, y-axis and z-axis is respectively month, year and exceeding-multiple(or exceeding-frequency). This technique makes pollutant's standard-exceeding characteristics such as exceeding severity and exceeding seasonal features very clear at a glance. Finally, the monthly, seasonal and annually changing trends of water quality time series were studied by means of Mann-Kendall test method.(4) According to the characteristics of structural complexity and non-stationary of the water quality series in the Yuqiao Reservoir watershed, water quality time series autoregressive model was built based on Markov switching theory. And then, Monte Caro method was introduce to combined with the above autoregressive model for Yuqiao Reservoir's water environment random simulating and risk evaluating.(5) The multivariate joint distribution model was applied to the risk combination quantitative analysis of the Yuqiao Reservoir's water environment system. And then, through analyzing the risk combination calculating results, the correlation among the key pollutants was studied.(6) The risk sources of the Yuqiao Reservoir's water environment system were identified based on the research conclusion of the previous chapter; and drew the conclusion that the eutrophication limiting fator of the Yuqiao Reservoir is phosphorus; and moreover, water algal blooming events in Yuqiao Reservoir during 7-9 month was chiefly caused by the release of phosphorus in the reservior's mud. Furthermore, the phosphorus release in the Yuqiao Reservoir mud is controlled by the Oxidation-Reduction of ferro element. At last, according to the risk source of the water environment, a set of countermeasures was put forward, which includes exogenous pollution risk countermeasurs, endogenous pollution risk countermeasurs, and emergency measures for algal blooming in the reservoir.