【作者】 谷尘勇；

【导师】 张智；

【作者基本信息】 重庆大学 ， 市政工程， 2005， 硕士

【摘要】 长江三峡工程是是举世瞩目的特大型水利工程，它的建成将在防洪、发电、航运等方面产生巨大的综合效益，同时也会对库区的生态与环境带来广泛而深远的影响。因此，三峡大坝投入运行后库区的水环境问题已经成为国内外环境保护工作者关注的焦点之一。 基于一维平流扩散质量迁移方程采用隐式差分解法建立的一维稳态水质模型，计算了三峡库区重庆段，从寸滩断面开始到市域出口结束共500km长江干流江段整体的水质特征。通过成库前一年2002年平水期参数率定和丰水期、枯水期参数验证，能较好的反映三峡库区重庆段水质变化趋势。在此基础上，并对成库后典型水流条件（坝前175m水位）下库区总体水质沿程变化趋势进行了预测。 此外还建立了一个二维随机水质模型，采用MonteCarlo方法求解。利用成库前平水期的长江黄沙溪段污染带的监测资料，对模型中横向扩散系数中的经验常数进行了率定，并利用枯水期污染带的监测资料，对率定的常数进行了验证，结果表明模型率定的经验常数反映了平、枯期长江黄沙溪段横向扩散系数的变化趋势，能较好的模拟黄沙溪岸边污染带的变化趋势。在此基础上，模拟了坝前水位175m时，三峡库尾黄沙溪段污染带的变化趋势。 研究结果表明： 对于COD_Mn、NH₃-N来说，虽然成库后断面平均流速降低，水深增加，COD_Mn、NH₃-N降级系数减小，但是由于库区流速减缓，COD_Mn、NH₃-N污染物在库区停留时间急剧增加，COD_Mn、NH₃-N污染物自净总量增大。同时由于重庆主城排水工程建成后，重庆主城的污染负荷减少，因而COD_Mn、NH₃-N成库后断面平均浓度比成库前降低。 成库后TP降解系数的影响较大，因TP降解系数只受水流条件的影响，成库后流速／水深的比值急剧减小使TP的降解系数急剧降低，对库区TP的净化不利。TP因重庆主城排水的建成，TP污染负荷降低，TP浓度略有改善。成库后TN、TP浓度已超过标准水平的富营养盐浓度。 在现有排污条件不变的情况下，黄沙溪段污染带在成库后有变长加宽的趋势，岸边环境容量减小，为保护岸边自来水厂取水口的安全，对重庆主城岸边排污口的设置及排污负荷提出更高的要求。更多还原

【Abstract】 The Three Gorges Project on the Yangtze River is the world-famous largest hydroelectric project. It will possess comprehensive utilization benefits for flood control, power generation and navigation improvement. But the construction of TGP will produce widespread and profound impact on ecology and environment. Therefore, the water environmental issue after the dam being put into practice has become one of the focuses not only domestically but also overseas.The one-dimensional water quality model which based on the one-dimensional advection-dispersion mass transport equation was developed. Then, it was applied to calculate the water quality characteristics of the Three Gorges reservoir in Chongqing region: that was the 500km-long mainstream beginning at Cuntan and ending at the boundary of Chongqing. The parameters of the model were proved to be validating by used the gauged values in the normal,dry and wet seasons. The validating result indicated that the model properly reflected the holistic water quality characteristics, showing its ability of prediction. Further, the model was applied to predict the water quality characteristics of the calculating zone at the time of completion of the project （175m water lever at the dam）.Meanwhile ,the paper established a two-dimensional random water quality model whose method of solution is MonteCarlo method. The empirical constant of the transverse diffusion coefficient was rating by used the gauged values of the pollution zone in the normal season in Huangshaxi of the Yangtze River. Then the empirical constant was verified by used the gauged values in the dry season. The validating result indicated that the model properly reflected the change of the pollution zone in the normal reason and the dry season , showing its ability of prediction. Further, the model was applied to predict the pollution zone in Huangshaxi of the Yangtze River at the time of completion of the project （175m water lever at the dam）.The research results showed that:Although the cross-section average velocity reduced, the water depth increased and the degradation rate coefficients of COD_Mn and NH₃-N reduced at the time of completion of the project （175m water lever at the dam）, the detention time sharply increased and total quantity of the self-purification increased. At the same time the pollution load of Chongqing city was reduced . the cross-section average COD_Mn and更多还原