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23 results on '"Dörfliger N"'

16. Importance of a high resolution lithological and geometrical knowledge for Mediterranean coast sedimentary aquifers management. Application to the Roussillon basin, South of France

Author

Aunay, Bertrand, Duvail, C., Le Strat, P., Dörfliger, N., Lachassagne, Patrick, Pistre, Séverin, Hydrosciences Montpellier (HSM), Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Université de Montpellier (UM)-Centre National de la Recherche Scientifique (CNRS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Laboratoire Dynamique de la Lithosphère (LDL), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), L. Araguás, E. Custodio, and M. Manzano

Subjects
well logging, Sequence stratigraphy, on-shore and off-shore geology, saltwater intrusion, Mediterranean sea, groundwater, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, Roussillon basin, hydrodynamic modelling, eustatism
Abstract

International audience; A good understanding of coastal aquifers is particularly important for their management and preservation,as well as for specific implementations (artificial recharge). A detailed knowledge of the lithology andgeometry of the aquitards and aquicludes is as important as that of the aquifers, particularly for seawaterencroachment dynamics. A new methodology, based on reservoir geology, is used to contribute to highresolutionlithological and geometrical knowledge of coastal sedimentary aquifers. The proposedmethodology is being applied on the Roussillon Basin, located along the southernmost part of the FrenchMediterranean coast, near the Spanish border. This basin covers an area of 700 km2 and comprises twoPliocene aquifers whose characteristics are linked to the Messinian event, and is overlain by the Quaternaryaquifer whose geometry is linked to eustatic variations. All these aquifers consist of alluvial and coastaldeposits. A detailed lithology and geometry model of this basin has been made mainly on the basis ofreservoir geology methods: (i) on-shore, through genetic stratigraphy and (ii) off-shore, through seismicstratigraphy. A detailed mapping of the elevation of the top and base of the aquifers andaquitards/aquicludes is thus available and will be used in a hydrogeological finite difference model. Thismodel will be used for various applications such as aquifer management, location of the outflow areas ofthe aquifers and sensitivity analysis on geometry (on-shore-off-shore).

Published
2004

23. Coastal groundwater salinization: Focus on the vertical variability in a multi-layered aquifer through a multi-isotope fingerprinting (Roussillon Basin, France).

Author

Petelet-Giraud E, Négrel P, Aunay B, Ladouche B, Bailly-Comte V, Guerrot C, Flehoc C, Pezard P, Lofi J, and Dörfliger N

Abstract

The Roussillon sedimentary Basin (South France) is a complex multi-layered aquifer, close to the Mediterranean Sea facing seasonally increases of water abstraction and salinization issues. We report geochemical and isotopic vertical variability in this aquifer using groundwater sampled with a Westbay System® at two coastal monitoring sites: Barcarès and Canet. The Westbay sampling allows pointing out and explaining the variation of water quality along vertical profiles, both in productive layers and in the less permeable ones where most of the chemical processes are susceptible to take place. The aquifer layers are not equally impacted by salinization, with electrical conductivity ranging from 460 to 43,000μS·cm(-1). The δ(2)H-δ(18)O signatures show mixing between seawater and freshwater components with long water residence time as evidenced by the lack of contribution from modern water using (3)H, (14)C and CFCs/SF6. S(SO4) isotopes also evidence seawater contribution but some signatures can be related to oxidation of pyrite and/or organically bounded S. In the upper layers (87)Sr/(86)Sr ratios are close to that of seawater and then increase with depth, reflecting water-rock interaction with argillaceous formations while punctual low values reflect interaction with carbonate. Boron isotopes highlight secondary processes such as adsorption/desorption onto clays in addition to mixings. At the Barcarès site (120m deep), the high salinity in some layers appear to be related neither to present day seawater intrusion, nor to Salses-Leucate lagoonwater intrusion. Groundwater chemical composition thus highlights binary mixing between fresh groundwater and inherited salty water together with cation exchange processes, water-rock interactions and, locally, sedimentary organic matter mineralisation probably enhanced by pyrite oxidation. Finally, combining the results of this study and those of Caballero and Ladouche (2015), we discuss the possible future evolution of this aquifer system under global change, as well as the potential management strategies needed to preserve quantitatively and qualitatively this water resource., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Published
2016
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