Nagels J W, Davies-Colley R J, Donnison A M, Muirhead R W
National Institute of Water & Atmospheric Research Ltd., (NIWA), P.O. Box 11-115, Hamilton, New Zealand.
Water Sci Technol. 2002;45(12):45-52.
Faecal bacterial dynamics during flood events were studied in the Topehaehae Stream near Morrinsville, New Zealand, in a catchment used for grazing dairy and beef cattle. During the rising limb of a natural flood event, E. coli bacterial concentration rose by more than 2 orders of magnitude and peaked at 41,000 cfu/100 mL. E. coli correlated closely with turbidity over the flood event, and both variables peaked close to the time of maximum flow acceleration rather than peak flow. An artificial flood on the same stream, created by releasing water from a supply reservoir during fine weather with no wash-in from the catchment, produced a broadly similar pattern of faecal contamination (peak E. coli = 12,500 cfu/100 mL). This and other evidence suggests that direct deposition of faecal matter by cattle in the stream channel may be of similar or greater importance than wash-in from land. The flood experiments have been useful for constructing a model of faecal bacterial yields, and they imply that exclusion of livestock from stream channels may appreciably improve water quality.
在新西兰莫林斯维尔附近的托佩哈埃哈埃溪流中，对一个用于放牧奶牛和肉牛的集水区在洪水事件期间的粪便细菌动态进行了研究。在一次自然洪水事件的涨水阶段，大肠杆菌浓度上升了两个多数量级，峰值达到41,000 cfu/100 mL。在整个洪水事件中，大肠杆菌与浊度密切相关，这两个变量在接近最大流量加速度而非峰值流量的时间达到峰值。在晴朗天气下，通过从供水水库放水制造的同一条溪流的人工洪水，且集水区没有冲刷进来的污染物，产生了大致相似的粪便污染模式（大肠杆菌峰值 = 12,500 cfu/100 mL）。这一情况及其他证据表明，牛在河道中直接排泄粪便可能比从陆地冲刷进来的污染物具有同等或更大的重要性。洪水实验对于构建粪便细菌产量模型很有用，并且这意味着不让牲畜进入河道可能会显著改善水质。
