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Incidence des bétoires et de la karstogenèse des plateaux crayeux de la Haute-Normandie sur le fonctionnement hydrologique de l'aquifère de la craie Modélisation hydrogéologique des influences climatiques à différentes échelles spatio-temporelles.

Abstract : Chalk plateaus in Upper Normandy are covered by chert-rich clayey residual formations resulting from chalk weathering and by Quaternary loesses. Altogether these covering layers may temporarily store and transmit water in the subsurface, then actinf like an epikarst. Chalk plateaus have a monotonous relief whereas they are also deeply incised by valleys. Plateaus represents more than 80% of the watershed area and are affected by the presence of many sinkholes. The chalk aquiferconstitutes a good example of covered karst where recharge modalities are complex and water resources quality may be affected by turbidity genretaed by superficial formations withdrawing and soil erosion. The main objectives of this thesis work are to understand the karstogenesis mechanisms at the origin of sinkholes and karstic network organization by defining the influence of the morphostructural characteristicss of the plateau on the modalities of the water level variability in the chalk aquifer. The ambition is then to calibrate a model of the spatial evolution of groundwater level in the chalk aquifer, taking into account the climatic signal based on the characteristics of the epikarstic system and the morphostructural regional context. We first determine the sensitive areas for the development of sinkholes (input karst), then we discuss the importance of the connections between the input karst and the output karst, identifying in particular the contribution of rapid karst-conduit water flow in subterranean watersheds dominated by regional aquifer flow. At the same time, we discuss the modalities of water transfer in the epikarst, including the role of surficial formations and sinkholes in the chalk aquifer recharge. The variations of hydrological signals are also analyzed in relation to the role of other hydrogeological parameters such as the aquifer thickness and the morphostructural context on groundwater flow. In this context, we demonstrate the heterogeneity introduced by the karstic drainage in the saturated zone and the influence of hydrological gradients on these heterogeneities using nitrates analyzes. Finally, these results were used to discuss and adapt a distributed regional ground water flow model in steady state conditions using the MARTHE model (©BRGM), coupled with the GARDENIA global model (©BRGM) in order to refine input data in MARTHE. The first results are satisfactory and prove the capability of the modelling approach to reconstruct water table, taking spatial karst-originating heterogeneity into account.
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https://tel.archives-ouvertes.fr/tel-00920267
Contributor : Valérie Casado-Malaizé Connect in order to contact the contributor
Submitted on : Wednesday, December 18, 2013 - 10:08:41 AM
Last modification on : Tuesday, October 19, 2021 - 11:33:55 PM
Long-term archiving on: : Wednesday, March 19, 2014 - 5:46:42 AM

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  • HAL Id : tel-00920267, version 1

Citation

S. El Janyani. Incidence des bétoires et de la karstogenèse des plateaux crayeux de la Haute-Normandie sur le fonctionnement hydrologique de l'aquifère de la craie Modélisation hydrogéologique des influences climatiques à différentes échelles spatio-temporelles.. Interfaces continentales, environnement. Université de Rouen, 2013. Français. ⟨tel-00920267⟩

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