Climate, Land and Environment, AgResearch Limited, Invermay Research Centre, Mosgiel, New Zealand.
Water Res. 2011 Apr;45(9):2863-74. doi: 10.1016/j.watres.2011.03.001. Epub 2011 Mar 15.
There is concern regarding microbial water quality in many pastoral catchments in New Zealand which are home to numerous livestock and wild animals. Information on microbial impacts on water quality from these animals is scarce. A framework is needed to summarise our current knowledge and identify gaps at the scale of an individual farm. We applied a Monte Carlo modelling approach to a hypothetical dairy farm based on the extensive data sets available for the Toenepi Catchment, Waikato, New Zealand. The model focused on quantifiable direct inputs to the stream from ducks, cows and farm dairy effluent (FDE) during base-flow conditions. Most of the inputs of Escherichia coli from dairy farms occur sporadically and, therefore, have little effect on the expected median stream concentrations. These sporadic inputs do however, have a strong influence on extrema such as 95th percentile values. Current farm mitigations of fencing streams and using improved management practices for applying FDE to land, such as low application rate deferred FDE irrigation systems, would appreciably reduce faecal microbial inputs to the stream. However, the concentrations of E. coli in rural streams may not reduce as much as expected as wild fowl living in streams would have a larger effect on water quality than a farm in which environmental mitigations are widely implemented.
新西兰许多以大量牲畜和野生动物为家的牧区集水区都存在对水质微生物的担忧。关于这些动物对水质的微生物影响的信息很少。需要有一个框架来总结我们目前的知识，并确定单个农场规模上的差距。我们基于新西兰怀卡托 Toenepi 集水区的大量可用数据集，应用蒙特卡罗建模方法对一个假设的奶牛场进行了研究。该模型侧重于量化在基流条件下鸭子、奶牛和农场奶牛废水（FDE）对溪流的可量化直接输入。来自奶牛场的大肠杆菌的大部分输入是零星发生的，因此对预期的中位数流浓度几乎没有影响。然而，这些零星的输入确实对极值（如 95 百分位值）有很强的影响。目前，农场对溪流进行围堵，并对 FDE 进行土地施用的管理措施进行改进，例如低应用率的延迟 FDE 灌溉系统，这将大大减少粪便微生物对溪流的输入。然而，农村溪流中的大肠杆菌浓度可能不会像预期的那样降低，因为生活在溪流中的野生鸟类对水质的影响会比广泛实施环境缓解措施的农场更大。
