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A full re-calculation of Water Framework Directive reference and target concentrations for German coastal waters and the western Baltic Sea is presented. For this purpose a spatially coupled integrative modelling approach is used, which links a river basin flux model with three-dimensional ecosystem model of the Baltic Sea. The years around 1880 are considered as reference conditions reflecting a high ecological status and simulated with the model system. For all monitoring stations the present day water quality derived from observations was than transfered to the historical situation by multiplying it with the calculated changes from model simulations covering the present and the pre-industrial situation. This was used to derive the reference concentrations of all necessary eutrophication parameters and by adding 50% to it, the needed target concentrations were derived on the scale of the single water bodies. By taking into account the specifics of every water body, this approach overcomes the inconsistencies of earlier approaches. Our targets are well in agreement with the targets needed for the implementation of WFD and MSFD. To reach the averaged targets, German nitrogen inputs have to be reduced by 34 %, resulting in an average maximum allowable concentrations in German Baltic rivers of 2.6 mg TN/l. To our results, MAI according to the BSAP (as Baltic-wide implementation of MSFD) may be sufficient for the open sea, but are not sufficient to reach a good WFD status in German coastal waters.

D5, Descriptor 5, Water Framework Directive, WFD, Baltic Sea, eutrophication, modelling, river basin flux model, pre-industrial,

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19/01/2016

Workshop of the Network of Experts for ReDeveloping Models of the European Marine Environment

OV

EN

201604260152

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