【作者】 唐莉华；

【导师】 胡和平；

【作者基本信息】 清华大学 ， 水利工程， 2009， 博士

【摘要】 水环境恶化是全球共同面临的问题,非点源污染是水体污染的重要来源,也是当前研究的热点和难点。采用水、沙、污染物耦合的流域水文模型进行非点源污染模拟,对深化流域水文循环、泥沙和污染物产生及输移转化过程的认识,提高流域水资源与水环境的综合管理水平有重要意义。流域水沙运动及其承载的污染物运移与地形地貌和生态之间是相互作用、相互影响的,论文基于地貌特征划分水文响应单元,在GBHM水文过程模型基础上,耦合泥沙和污染物的运动过程,建立了流域水-沙-污染物耦合机理模型GBHM-CWSP,对流域水文过程、土壤侵蚀和泥沙输移以及污染物迁移转化过程采用物理性的方程进行描述,可体现地貌特征对流域水文、泥沙和污染物运移过程的控制性作用,在保持机理性和模拟精度的前提下减少计算量。分析了张家坟水文站多年径流泥沙资料,认为土石山区土壤侵蚀产沙受“侵蚀能力”和“可侵蚀量”双重控制,在土壤侵蚀和河道冲淤动力学模型中增加“可侵蚀量”作为实际土壤侵蚀量和河道冲刷量的阈值,改进了流域泥沙运动的模拟。根据土壤溶质向坡面径流中的输出及其在土壤中运移的不同机制,构造了降雨径流与土壤水的交换函数,建立径流层、混合层和土壤层的水分溶质耦合运移方程,将土壤中污染物垂向运动与流域地表径流中沿坡向运移结合,建立了机理性流域坡面单元污染物运移模型。论文以潮白河流域为研究对象,建立了水-沙-污染物耦合模型,并利用下会、张家坟两个水文站的径流和水质实测数据进行模型的率定和验证。应用GBHM-CWSP模型,采用情景模拟方法分析了潮白河流域1980-2005年的径流、泥沙和污染负荷变化趋势及其与土地利用、气象要素变化之间的关系。研究表明,气象要素变化是引起径流、泥沙和氮磷污染负荷变化的主要原因,其贡献率分别为92%、95%、51%和70%。论文还应用GBHM-CWSP模型,对IPCC提供的两种未来气候情景模式下潮白河流域径流、泥沙和氮磷负荷量进行了预测。更多还原

【Abstract】 One of the most challenge issues in the current work is the scarce of water resources, and the serious pollution of water bodies enhance such situation, of which the non-point source pollution (NPSP) contributes the most significant portion. The NPSP topic received a lot of research interesting during the past several decades, and mathematical simulation approach of coupled water, sediment and pollutant serves as not only a way to understand the mechanism and processes of pollution, but an effective tool in basin management and environmental protection.The coupled processes of water, sediment and pollutant in watershed are dominated by geomorphological features. In this paper, a distributed hydrological model coupling water, sediment and pollutant at the catchment scale based on geomorphological features is developed, which named as GBHM-CWSP, after current GBHM model by Yang et al. (1997). The GBHM is used to simulate hydrological process, and the other processes including erosion over hillslope, sediment routing in stream, pollutant discharge between soil and runoff inter-face, pollutant transport and transformation in soil profile and in stream, are all coupled in this integrated model. In GBHM-CWSP model, the physically based equations are used to describe most aspects of water, sediment and pollutant. Moreover, geomorphological similar elements are used as discretization and simulation units based on DEM, which make the computation more rapidly and effective than regular division as grid cells.The characteristics of sediment yield in rocky mountain area is greatly different from that in loess area, because the sediment quantity is limited, which may cause a phenomenon of“sediment exhaust”after a heavy storm event, and not accumulated enough for erosion in the next storm. Therefore the“potential of erosion quantity”is used to control the actual erosion in hillslope unit and in stream. By this way the simulation result will be more precise. In the simulation module of pollutant movement in hillslope unit, an exchange function between water soil and runoff is constructed to depict the solute discharge from soil to runoff at the soil-water interface during rainfall-runoff. The convection- dispersion equation (CDE) is adopted to describe the solute transportation on the soil profile. The combining of mechanic equations in large-scale basin model enhance the physical basis.The Chaobai river basin, located in the upstream of Miyun reservoir, is chosen as case study area in this paper. Based on the DEM, landuse, soil data, etc., the GBHM-CWSP model is build up. After the calibration and validation by observed data of runoff, sediment, nitrogen and phosphorus loadings from 2000 to 2005 at two stations: Xiahui and Zhangjiafen, this integrated model is applied to analyze and identify the effects of changes of landuse-cover and climate factors on runoff, sediment, nitrogen and phosphorus loadings. By scenario analysis, the contributions of landuse change and climate factors change are evaluated. The results show that the change of climate factors has predominant contribution to runoff and sediment changes, both more than 90%. While for nitrogen and phosphorus, the effect of climate factors changes is decreased as 51% and 70% respectively. Especially for nitrogen, the farmland is the major source of nutrient loss, thus landuse changes have significant effects on nitrogen loadings. Using GBHM-CWSP model and IPCC data, an attempt of prediction of runoff, sediment and pollutant loadings in the future in Chaobai river basin is performed.更多还原