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流域水质管理是一个多步骤的过程,数学模型以其定量计算和动态操作在流域管理中起着重要作用。本文利用美国农业部开发的AnnAGNPS模型,以大沽河典型小流域为例,给出非点源污染流域水文水质模拟过程。首先在集水单元和沟道勾划的基础上,完成数据库的建立。参数估值主要依据流域性质、先前经验值、其它模拟研究和文献中的取值。其次采用各小流域出口流量、泥沙和总氮实测值优化参数、校准和验证模型,分析模型在研究区的适用性。在大沽河小流域,模型对降雨场次地表径流、泥沙及总氮的模拟结果表现出了很大的不确定性,而相应的年均负荷估算结果较好。当前AnnAGNPS模型主要被用于评价流域非点源污染的长期影响及最佳管理措施的选择,以上精度足矣。最后利用校准后的模型进行小流域污染负荷估算和管理措施模拟。结果表明为了达到同时削减径流、沉积物及总氮的输出量,在大沽河上游应采取退耕还林的措施,治理非点源污染。
Basin water quality management is a multi-step process. Mathematical models play an important role in watershed management with their quantitative calculation and dynamic operation. In this paper, the AnnAGNPS model developed by the United States Department of Agriculture is used to take a typical small watershed in Dagu River as an example to give a hydrological and water quality simulation process of non-point source pollution. First of all, on the basis of water catchment unit and channel delineation, the establishment of the database is completed. Parameter estimates are based primarily on the nature of the catchment, previous experience values, and other simulation studies and literature values. Secondly, the optimization parameters, calibration and validation models of outlet flow rate, sediment and total nitrogen measurements were used to analyze the applicability of the model in the study area. In the Daguhe watershed, the model shows a great deal of uncertainty in the simulation results of surface runoff, sediment and total nitrogen in the rainfall field, and the corresponding average annual load estimation results are good. The current AnnAGNPS model is mainly used to evaluate the long-term impact of non-point source pollution in watersheds and the selection of the best management practices, all of which are accurate. Finally, using the calibrated model to simulate the pollution load of small watershed and management measures. The results show that in order to achieve the simultaneous reduction of runoff, sediment and total nitrogen output, the upstream of Dagu River should take the measures of returning farmland to forest to control non-point source pollution.