International audienceSince 2000, the European Water Framework Directive has required managers to restore water bodies to good ecological status, including rivers that have been substantially anthropomorphized, i.e. the vast majority of rivers in France. This obligation creates situations, such as removal of mill sluice gates and strong resistance from local stakeholders that must be addressed by governmental agencies and local elected officials. Seine watershed researchers have suggested using a hydraulic model to give river managers an overall vision of structure function (including sluice gates) and the water elevation adjustments between the upstream and downstream reaches with adjustments to the structures. Scientists adapted their model with the collaboration of the local actors in charge of the river management. This simulation of the management of river structures was achieved by constructing an interactive platform and using it to simulate annual flow scenarios for the river and management objective scenarios for all types of use, both recreational and high- and low-water scenarios. Model construction and simulation reunited scientists; State services agents, elected officials but also mill owners and members of local associations. The objective of this collective use was to allow managers to appreciate the current knowledge on the effects that removing a structure would have, around a multifunctional approach to the river, to consider removal of certain structures depending on the locally expected results

Cet article repose sur l’analyse de 490 reportages de journaux télévisés ayant pour sujet les « algues vertes » en Bretagne diffusés entre 1986 et 2015. La présentation du problème a évolué au cours des trente dernières années, perçu tour à tour comme un frein au tourisme dû aux pollutions urbaines, une catastrophe écologique causée par le productivisme agricole et enfin un nouveau gisement pour le développement durable des territoires. Les médias bousculent l’agenda politique régional et, ce faisant, précipitent la remise en cause du « modèle agricole breton ».

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