[Approximation of the dynamics of microbial contamination of the Segre River in Lérida]

The water rivers contains a basal autochthonus population of micro-organisms which is local and temporal and it is modified by the incoming sewage. In this paper a simple model is applied to estimate the faecal bacterial load poured from the town of Lérida to the Segre River and the downstream assimilation capacity of this river. In spite of the inherent limitations and imprecision due to sampling operations and calculations, the numerical results are related to other published results. The evolution of faecal bacterial population downstream of Lérida does not follow the theoretical model without a growth coefficient. The showed data on faecal pollution (bacteriological and viral detectors) are the only ones which have been published on the final section, the most disturbed, of the Segre River.