La notion de limnicité est-elle suffisante pour caractériser l’empreinte spatiale et sociétale des plans d’eau?

Abstract : The present article has for aim to discuss genesis and limits of « limnicity » notion in relation to new social and societal problems, arise from many lacks of understanding between legislator and ground actors about water masses notions of ECD law. Those limits are numerous and already visible even in the structure of actually water's layout tools. Indeed, as part of ECD law application, French water agencies take into account « MEFM » (water masses which are so much modified) besides lakes even though they aren't naturals. So, it's a first transgression. It added to this the area threshold: without any limnic argument, this one is fixed at 50 hectares, while bidder the liberty of interpretation considering local realities (reduction of threshold, lacustrian regions). Those choices have two consequences: firstly, the criterion of single lacustrian naturalist is jeopardize and the area arbitrary leads to a conflict on ground between water actors (less than 1 % of French water bodies are identified, the rest being considered by default as river section); secondly, the priority criterion of area is called into question by numeric notion specific to lacustrian regions. The authors intend to adapt the « limnicity » notion to the lentic complexity and take into account all the lakes and man-made seas and, in parallel, increase the range of water bodies studied in integrating ponds which, at the scale of France, have a higher total area than that of lakes: so a new notion arises of this, the « extended limnic ratio ». Then, the choice of water body's spatial scope for dominant criterion is debated over linked with scientists progressives which highlight the pregnancy of lacustrian fact rehearsal compared to the impact of only one limnic object, whether it is the physical chemistry factors of water or societal plan. Also, water body's density is placed on the same analysis level than the water body's surface area. Thanks to this scientist development, two new indicators are produced allowing bettering understanding the role of water bodies in the environment: the equal surface area subscript (ESS) and the equal concentration subscript (ECS). Applied to French department scale, those two indicators highlight a major fact : the department which own the more recognizes lacustrian regions as well national as international, and which ones actually managements are decided, are secondary for the comprehension of social and environmental links existing actually at the water body's level. This analysis shows how much there is discrepancies between water body's ground reality and those imagined, and the only one notion of « limnicity » can't be able to bring out alone.
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Submitted on : Wednesday, March 27, 2019 - 12:41:30 PM
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Pascal Bartout, Laurent Touchart. La notion de limnicité est-elle suffisante pour caractériser l’empreinte spatiale et sociétale des plans d’eau?. Revue Géographique de l'Est, Association des géographes de l’Est, 2016, 56 (1-2), ⟨http://journals.openedition.org/rge/5766⟩. ⟨hal-02081153⟩

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