【作者】 张超；

【导师】 王兴奎；

【作者基本信息】 清华大学 ， 水利工程， 2008， 博士

【摘要】 中国正面临着严重的水质危机,大量湖泊、水库处于富营养状态,直接威胁到饮用水安全。三峡水库运行后所造成支流水体富营养化问题已经显现,一些支流开始发生水华现象。在点源污染逐步得到控制的情况下,非点源的氮、磷的汇入便成为富营养化的重要因素。构建流域分布式非点源污染模型是对流域泥沙、污染物进行量化,并研究它们的变化规律的有效方法。本文首先参照分布式水文模型的通用框架,建立了能够描述土地覆被、土壤水力特性的坡面单元产流计算子模型和河网汇流计算子模型,然后将土壤侵蚀/输移模型和污染物输移模型嵌入到两个子模型中,形成分布式非点源污染模型,在总体框架的构建方面取得了新的发展。对分布式非点源污染模型的支撑技术进行了系统研究:以数据结构中的多叉树理论为基础提出了自动建立子流域拓扑关系的新算法;采用“+1”分级与Strahler分级的河网生成算法,实现了同级河段的多线程并行汇流计算及扩散波与动力波汇流计算的自动搭接。利用Visual C++开发环境结合GIS、数据库和多线程并行计算等多种技术,开发了综合计算平台。该计算平台具备了通用模型系统的基本功能及扩展功能,即前处理、模型计算、后处理功能,重视功能模块间的组织和配合,具有较强的适应性和可扩展性。平台的数据自动提取、制备功能得以增强,支持基于数据库和基于文件的数据流模式,能够支持Access、Oracle多种流行数据库格式。坡面计算采用多线程并行计算机制,能充分发挥多核计算机的工作效能。选取香溪河流域作为研究对象,收集整理了流域内的水文、气象、土地、植被等数据,同时计入工业、农业及生活排水量和排污量,对流域内的水文动态过程进行了模拟,并与流域内的兴山水文站的资料进行了对比验证。在水文模拟的基础上,对土壤侵蚀和氮磷污染负荷的变化过程、规律进行了模拟研究。结果表明,流域内的土壤侵蚀量与短时降雨强度正相关;月平均总氮浓度与降雨量存在明显的正相关,而月平均总磷浓度则主要受人类生产生活的影响;三峡蓄水后,随着污染物在香溪河库湾内的蓄积,库湾内的水质将有可能进一步恶化。更多还原

【Abstract】 China is now faced with a nation wide water quality crisis, as eutrophication keeps invading and suffocating an increasing number of lakes and reservoirs. The Three Gorges reservoir, for example, has seen eutrophication occurrences in tributaries of the upper Yangtze due to point and non-point source pollution. With point source pollution being gradually put under control, the non-point source (NPS) pollution (nitrogen and phosphorus) stands as the major issue that needs to be addressed to help prevent or combat possible large scale eutrophication in the reservoir.A distributed NPS pollution model is developed to quantify sediment erosion, pollutants transportation, as well as to study changing law of pollutant loads. Based on the main frame of the distributed hydrology model, this model incorporates a sub-model for calculating runoff in the slope under various land cover, with a second sub-model for flow routing in river networks. Soil erosion/sediment transportation and pollutants transportation sub-models are also added to the above mentioned 2 sub-models, composing the integral distributed NPS pollution model. New advance in construction of the overall frame has been achieved.Systematic research is made on the supportive techniques for developing NPS pollution model. Starting from the multiple tree theory, a new algorithm for automatic topology among the sub-basins is put forward; parallel routing based on the automatic hierarchical organization of river networks, namely the Plus One ranking, is achieved. Additionally, the automatic joint usage of diffusive/dynamic wave method for rooting is implemented.An integrated application DWHEMT is developed with Visual C++, supported by GIS, database, multi-thread parallel calculation techniques. The application has basic and expanded functions of common model systems, including pre-processing of raw data, model calculation and post-processing of results. With much attention being paid to the organization and cooperation among the modules of function, the adaptability and expansibility of the application are enhanced further. The application has enhanced automatic data extraction and preparation capabilities. It supports both database and file based data exchange modes, and is also compatible with many popular database formats such as Access, Oracle etc. The multi-thread parallel calculation mechanism is adopted by slope unit calculation, which can exert the capacity of a multi-core PC to its full content.The Xiangxi River watershed is chosen as the case area. After the collection and preprocessing of DEM, image materials of remote sensing of land use and land cover, categorized distribution map of soil, hydrology data, meteorological data etc, a simulation of dynamic hydrological process is carried out and an example in Xingshan Hydrologic Station is served. On the basis of hydrology simulation, the variation processes and changing laws of sediment and total nitrogen and phosphorus within the Xiangxi River Watershed is studied. The results show that the soil erosion in Xiangxi River watershed has the positive correlated to the rainfall intensity in short-term; there are obvious positive correlation between monthly average total nitrogen concentration and rainfall, while the monthly average total phosphorous concentration is more deeply affected by human; the enhanced deposition and dilution effect, caused by the impoundment of Three-gorge Reservoir, are temporary. As the accumulation of pollution goes on in the gulf, the water quality there would probably continue deteriorating.更多还原