Modelling faecal coliform dynamics in streams and rivers

A series of field experiments are reported which have provided empirical evidence to improve the understanding of faecal coliform entrainment mechanisms within stream channels. A new conceptual model of faecal coliform dynamics is proposed and preliminary modelling results presented. The model is based on the assumption that the entrainment and deposition of organisms from storage within the stream bed is governed by the relationship between flow and the channel bed. The organisms are assumed to be associated with particulates of low settling velocity. Channel bed storage is modelled by a series of longitudinal sub-store units which are sequentially accessed as flow rises, each store unit is rapidly depleted of organisms after the onset of entrainment. Deposition to sub-stores where entrainment is not occurring is assumed to occur at a constant rate. Further investigations are required to confirm the results and examine the application of the model to natural flow events or alternative determinands.