农业非点源污染模型AnnAGNPS适用性检验

以大沽河典型小流域为研究区,借助GIS和相关资料提取参数,建立模型数据库。在此基础上,采用2001～2002年小流域出口径流量、泥沙和总氮监测数据优化参数、校准和验证模型,分析AnnAGNPS模型在大沽河典型小流域的适用性。结果表明,模型对日均径流量、泥沙及总氮输出的模拟能力较差,而对年均污染负荷估算结果比较理想。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精度足矣。

EVALUATION OF SIMULATION OF AnnAGNPS MODEL

Surface waters can be polluted by emissions and discharges from two main types of pollution sources,namely the point sources and non-point sources.While point sources are for the most part well characterized and regulated by permission,the emissions and discharges of non-point sources,which are more difficult to trace and characterize,have been increasingly recognized as significant sources of pollution.Non-point source pollution models are considered as a cost-effective and time-efficient method for the assessment of pollutant loads,simulation of watershed processes,and selection of management practices in an effort to address non-point source pollution.AnnAGNPS and its single event predecessor AGNPS have been widely used for non-point pollution management over wide range of environments.While the evaluation and application of AnnAGNPS model has been focused on Zhejiang and Fujian Provinces in the coastal region of Southeast China,no attempt has been made to utilize the model in eastern zones where surface and ground water is seriously impacted on account of the intensively agricultural actions by inhabitants.A study was undertaken to lay out the steps of water quality simulation selecting a 610.81km2 upper watershed located on the Shandong Peninsula of China as a case.The attributes of watersheds,tributary channels,and the main channel in each cell were generated using ArcView-AnnAGNPS interface.And then the model was separately calibrated and validated using observed data in the outlet of watershed during the period of 2000～2001 years.While predicted and observed runoff,sediment,and total nitrogen on a daily basis were poorly correlated,the corresponding results on annual basis were performed reasonably well.Although some deviation existed between observed and estimated constitutes,the overall trend can be obtained for runoff,sediment loads,and total nitrogen by model,which illuminates that AnnAGNPS may be more suitable for comparative assessments of alternative management and policy scenarios and for gross estimation of nutrient loads.Above results confirmed that the AnnAGNPS model could be applied for East China.Nevertheless the need of detailed exploration of more extensive data should be especially focused,e.g.ascertaining the effects of short-term rainfall intensity and space variation on the model results due to the poor simulating accuracy for rainfall event of small magnitude.It is thus expected that the applicability for China can be improved additionally by creating a national parameter database through collecting experiences from all applications in similar conditions as well as modifying the method of estimation for sediment yield and total nitrogen.