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Obstacles and facilitations for the movement of fishes

May 05, 2010 / alpMedia
An inventory of all the artificial barriers that impede the flow of rivers has found out that French rivers are interrupted by 60,000 dams, weirs, locks, mills etc. The inventory has been recently published as a online map where the works are shown divided by department, municipality or watercourse. All these works obstruct the movement of migratory aquatic organisms and the transport of sediments, thereby affecting ecosystems.
Image caption:
Modern art? The first impression deceives: it is a detail from an online map showing the obstacles on the French rivers. © IGN/Agence de l'Eau/Ministère en charge de l'Ecologie 2009
In some cases, these barriers are inconsistent with the objective set by law on the rivers and aquatic environments (LEMA), which is to put watercourses in good ecological conditions by 2015.
The Institute of the University of Kassel (D) has developed a new kind of facility that, through the use of pumps, creates a flow able to attracts fishes. With an injector a more intense flow is created at the entrance of the fish pass, that is exactly where it is needed. In this way, fishes can find more easily the entrance of the artificial pass without having to use more water to feed the fish pass. Moreover, special barriers made of synthetic material ease further the entrance of the fishes in the right canal and prevent them from ending up in the canal that feed the turbines.
Map of the barriers: (F), (F), (D)