Collins Rob, Rutherford Kit
National Institute of Water and Atmospheric Research, P.O. Box 11-115, Hamilton, New Zealand.
Water Res. 2004 Feb;38(3):700-12. doi: 10.1016/j.watres.2003.10.045.
A model has been developed to predict concentrations of the faecal bacteria indicator E. coli in streams draining grazed hill-country in New Zealand. The long-term aim of the modelling is to assess effects of land management upon faecal contamination and, in the short term, to provide a framework for field-based research. A daily record of grazing livestock is used to estimate E. coli inputs to a catchment, and transport of bacteria to the stream network is simulated within surface and subsurface flows. Deposition of E. coli directly to streams is incorporated where cattle have access to them, and areas of permanent saturation ('seepage zones') are also represented. Bacteria are routed down the stream network and in-stream processes of deposition and entrainment are simulated. Die-off, both on land and in water, is simulated as a function of temperature and solar radiation. The model broadly reproduces observed E. coli concentrations in a hill-country catchment grazed by sheep and beef cattle, although uncertainty exists with a number of the processes represented. The model is sensitive to the distance over which surface runoff delivers bacteria to a stream and the amount of excretion direct to streams and onto seepage zones. Scenario analysis suggests that riparian buffer strips may improve bacterial water quality both by eliminating livestock defaecation in and near streams, and by trapping of bacteria by the riparian vegetation.
已开发出一个模型，用于预测新西兰放牧山地集水区溪流中粪便细菌指标大肠杆菌的浓度。该建模的长期目标是评估土地管理对粪便污染的影响，短期内则是为实地研究提供一个框架。利用放牧牲畜的每日记录来估算集水区内大肠杆菌的输入量，并在地表和地下水流中模拟细菌向河网的传输。当牛能够接触到溪流时，将大肠杆菌直接沉积到溪流中的情况也被纳入模型，同时还考虑了永久饱和区域（“渗流区”）。细菌沿着河网流动，并模拟了河水中的沉积和夹带过程。在陆地和水中的死亡情况被模拟为温度和太阳辐射的函数。尽管所描述的一些过程存在不确定性，但该模型大致再现了绵羊和肉牛放牧的山地集水区中观察到的大肠杆菌浓度。该模型对地表径流将细菌输送到溪流的距离以及直接排泄到溪流和渗流区的粪便量较为敏感。情景分析表明，河岸缓冲带可能通过消除溪流及其附近的牲畜排便以及通过河岸植被捕获细菌来改善细菌水质。
