MODELING FECAL-COLIFORM DYNAMICS IN STREAMS AND RIVERS

A series of field experiments are reported which have provided empiric al evidence to improve the understanding of faecal coliform entrainmen t mechanisms within stream channels. A new conceptual model of faecal coliform dynamics is proposed and preliminary modelling results presen ted. The model is based on the assumption that the entrainment and dep osition 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. C hannel bed storage is modelled by a series of longitudinal sub-store u nits which are sequentially accessed as flow rises, each store unit is rapidly depleted of organisms after the onset of entrainment. Deposit ion to sub-stores where entrainment is not occurring is assumed to occ ur at a constant rate. Further investigations are required to confirm the results and examine the application of the model to natural flow e vents or alternative determinands.