Modélisation de la qualité de grands cours d'eau Eutrophisation : cas de la Moselle et du Doubs

Modelling of the quality of large water courses: eutrophication, the case of Moselle and Doubs rivers

¹ Direction des études et recherches EDF, Chatou
² Agence de l'eau Rhône-Méditerranée-Corse, Pierre-Bénite
³ Agence de l'eau Rhin-Meuse, Moulins-Les-Metz

Abstract

In many big rivers at the low-water mark major phytoplankton or microscopic algae development can be seen living and being moved along by the current.

Unlike what is seen in many lakes at the end of Spring this algae development does not usually exhaust the stock of easily assimilated phosphorus contained in the water. Thus phosphorus is not a factor that limits the growth of phytoplankton and this is why we have the proliferation of plant life if other nutrients are not lacking. Since digital modelling is capable of taking into account hydrometerological conditions over several years it is an efficient instrument for assessing the reduction of waste being introduced into the catchment area that is necessary in order to obtain limiting conditions. Applications are given for the Doubs and the Moselle rivers for which we show that a large scale dephosphatization effort would be required in order to achieve a major reduction in the concentration of phytoplankton.