Modelisation of a lotic ecosystem polluted by a pigsty waste : hydrodynamic and transport mecanisms
A simulation model of organic carbon movement was designed for a river polluted by piggery wastes. The physical dynamics of this model, as described in this paper, include a hydrodynamic component inspired by a Saint Venant's model coupled with a transport model based on the classical advection-diffusion equation. The model is applied to unidirectional, non-uniform, unsteady flow conditions. The equations were solved by a finite difference method using implicit schemes. The parameters of the equation were adjusted to fit flow conditions determined with a rhodamine dye tracer. When applied to the dissolved organic carbon transport in the Albenche river, the model showed that the distribution of organic carbon in space and in time was due to physical processes only. The differences in concentration between the observed and the expected values in the downstream station could represent the consumption of benthic biotic organic carbon.