Fonctionnement hydrologique des têtes de bassin versant tourbeuses du Nord-Est du Massif Central

Abstract : After decades of neglect and total destruction by drainage and extraction of peat, mires have finally been considered over the last ten years as ecosystems of major interest, both in terms of water resources that they store, the biodiversity they contain, and paleoenvironmental records they retain. However, knowledge of the hydrological functioning of these wetlands remained incomplete. Apart from the works of the eighteenth and nineteenth centuries, we rediscovered during the study that the French scientific publications on this issue are rare. This work was part of research programs launched in the Eastern Massif Central with the dual objective of ensuring missions including basic research for a better understanding of water bogs and answering questions from managers engaged in conservation and restoration of the wetlands. Due to the lack of data on the current dynamics of mires from the north-east of the Massif Central, the selection of pilot peatlands and their watershed for the establishment of the experimental procedure is an important part of this work. Despite the funding and support of communities, the acquisition, installation, configuration and maintenance of measuring devices, abused by harsh climatic conditions, were the main difficulty in this study. In these pages, we discussed in two parts the problematic of hydrological role of mires. First we show how the hydrological functioning of peatlands complies with selected models available within the important international literature, mainly Anglo-Saxon. Then we assess the impact of the presence of mires at the level of heads of watersheds. The bogs as well as the fens are large stocks of water. The main results highlight the uniqueness of peatlands towards the restoration of water coming into their surface. They affect the volumes of water evaporation, stored and disposed of. Their ability to absorb water in the acrotelm, promoting flow desynchronization, gives them a regulating role which effectiveness varies during the hydrological years. However, beyond their intrinsic storage capacity, which depends on the geometry of the bog (i.e. shape, size, thickness), peatlands even small in size due to their position, may affect the dynamics of water catchments areas. Exchanges between these saturated zone, in which the water flow is very slow and the slicks side are weak, may constitute hydrological locks which limit the speed of groundwater discharge and support rivers flow. The results of this study finally allow to state, in terms water resources management, that a global consideration of the mires at the level of watersheds is very much needed.
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Submitted on : Friday, January 23, 2009 - 10:44:47 AM
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Jérôme Porteret. Fonctionnement hydrologique des têtes de bassin versant tourbeuses du Nord-Est du Massif Central. Géographie. Université Jean Monnet - Saint-Etienne, 2008. Français. ⟨tel-00355560⟩

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