Modelling the impact of a stormwater inflow on Escherichia coli densities in an urban shallow lake
Résumé
Urban lakes provide many ecosystem services including recreational activities. These lakes can be contaminated by waterborne pathogens from various sources, such as storm sewers. As a consequence rain events can affect the lake microbial quality. However, little is known about t he factors that impact the fate of pathogens, and the duration of the contamination. In order to address this issue, Escherichia coli, a fecal indicator bacterium, was quantified in the stormwater inlet of Lake Créteil (France).
During a 6month period (June to December 2013), six storm events were monitored. E. coli concentrations were measured in integrated samples of the inflow and in samples collected 6 hours later in the lake along a spatial gradient. Water temperature, current velocities and E. coli concentrations were computed using the 3D hydrodynamic model Delft3DFlow.
The model was calibrated with one storm event and verified with the other events. Simulation results reproduced the plume extension and theobserved E. coli concentrations. The model provided useful outcomes on the extension of the plume, its motion, the time, location and duration of E. coli peaks. These results show that a 3D hydrodynamic model can be used to infer the spacetime representativeness of discrete monitoring.