Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Result related to Thau Lagoon

DITTY project produced several new management tools for the Thau lagoon and contributed to establish links or to strengthen the existing ones between administrative bodies, scientific institutions, universities and technical agencies. During the project, more than 30 meetings were organized. In order to complete the DITTY database (WP1), data description, standardization and intercalibration were performed. Relational databases developed under previous national or regional projects (PNEC "Chantier Lagunes mediterraneennes", SYSCOLAG, etc) were taken into account within the framework of DITTY project. The conception and the building up of an operational Observatory envisaged for the Thau lagoon and its watershed will benefit from DITTY inputs.

A coherent GIS for Thau lagoon, its watershed and its connections with the sea was built up (WP3). GIS applications implied the integration of data compiled under WP1, results from SWAT and MARS-3D models (WP4) and spatialized environmental and socio-economic indicators developed according to the scenario analysis (WP6, WP7) with the view to set up the DSS (WP8).

Among the specific products derived from the integrated approach based on GIS we may list i): development of a monograph on the Thau lagoon and its watershed based on a set of validated GIS maps ii): setting up of spatial indicators for the watershed and the lagoon as regard the microbiological contamination case study. Concerning comparative analysis (WP5), inter-comparison and benchmarking of COHERENS and MARS-3D models showed a good fit between hydrodynamic variables simulated with both models. Inter-comparison between the 5 sites was carried out by JRC-IES partner using the IFREMER classification scheme established for the French Mediterranean Coastal lagoons, which was aiming at implementing an operational tool for the assessment of the eutrophication of French Mediterranean lagoons (RSL network: Resau de Suivi Lagunaire). The results achieved offered good prospects for the generalisation of such an approach within the framework of the European Water Directive for Transitional Coastal Waters. The end-users gave a high priority to the microbiological contamination of the Thau lagoon's water and shellfish. Thus most of effort was concentrated on the effects of bacteria of sanitary concern.

The main challenges were
(i)to define the transfer functions for the rivers outlets along the lagoon coastline,
(ii) to define the fluxes taking into account the meteorological conditions and the regulations with reference to the water quality and,
(iii) to identify areas in the lagoon which are microbiologically contaminated and to assess the economical consequences. Significant results were obtained in this respect by the project.

A specific methodology was developed in order to characterise and simulate effects on the lagoon of microbial contaminants originated from wastewater systems and urban development in the watershed. The existing MARS-3D hydrodynamic model and its biological module were used to define for each river outlet on the lagoon, a "Maximal Allowable Flux" (MAF) as the threshold for inputs flux values above which shellfish farming zones are considered under bacteriological contaminants impacts. These results (obtained in WP4 and WP8) were discussed with end-users from a management point of view. It is effectively necessary to estimate bacterial fluxes that really flow into the lagoon during flood events and to compare the values observed to the MAF. If, for a given river, the flux is below the MAF, no improvement of the wastewater processing infrastructures in the watershed is necessary.

If observed fluxes are higher than the MAF values, management options on wastewater treatment plants (or others works) can be proposed and simulated to find the more efficient way to reduce the bacterial fluxes. A Decision Support System was developed for the Thau lagoon in order to establish, according to budgetary, socio-economical and environmental constraints, different scenarios required by the end-users. These scenarios could then be ranked according to the specifications of the end-users. A new programme called OMEGA THAU was launched at the end of 2006, with the view to explore new management tools and to forecast environmental crisis using early warning systems.

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