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Modelling fecal bacteria in the Scheldt river and estuary

par de Brauwere, Anouk;Passerat, Julien ;Servais, Pierre ;Deleersnijder, E.;Gourgue, O.;de Brye, B.
Référence European Geosciences Union General Assembly 2008(13-18 April 2008: Vienna, Austria), Geophysical Research Abstracts, Vol. 10, EGU2008-A-00720, 2008, Copernicus Publications, Vol. 10
Publication Publié, 2008

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Résumé :

With its population density of over 500 inhabitants per km2, its active industrial developmentand its intensive agriculture and animal farming, the Scheldt watershed representsan extreme case of surface water and groundwater pollution which in turn hasan impact on eutrophication and the ecological functioning of the receiving coastalwaters. A Belgian interuniversity collaboration (http://www.climate.be/TIMOTHY)has recently started, aiming to better understand past, present and future changes inthe quality of surface, ground and marine waters and to relate them to changing humanactivities on the watershed. Part of the originality of the new network resides inthe coupling of existing hydrodynamical and biogeochemical models to describe thetransport and transformation of nutrients and contaminants.One of these couplings consists of connecting an ecological module to the SecondgenerationLouvain-la-Neuve Ice-oceanModel (SLIM, http://www.climate.be/SLIM).The results of a first application will be shown, where the ecological module considersthe dynamics of one fecal bacteria indicator (Escherichia coli). The power of SLIMis that it solves the governing hydrodynamical equations using finite elements on anunstructured mesh. As such it is able to accurately model the different scales in thedomain, going from the Scheldt river, over the estuary (including the special featureof sand banks being periodically submerged), to the North Sea.This modelling exercise illustrates the combined effect of hydrodynamics, mortalityand sedimentation on the abundance of E. coli in the study domain - with a resolutionthat is impossible to achieve by sampling alone. However, in order to have a reliableand accurate tool, much effort was put on data gathering and the optimal incorporationof this information (e.g. for the initial and boundary conditions, for the estimation ofmodel parameters, or for validation). In addition, the first modelling results helpedto guide future sampling campaigns such that data and modelling can be optimallyadjusted and a maximum of information can be retrieved.Although the hydrodynamical model and its coupling to an ecological module may beof scientific interest on their own, it is even more attractive that their output can beinterpreted in terms of practical needs, i.e. the abundance of fecal indicators which aredirectly related to sanitary risk and standards for water quality. In this framework, themodel is also intended for assessing the effect of different scenarios for the future, andadditional pollution indicators will also be included in the ecological module.