Voici les éléments 1 - 5 sur 5
  • Publication
    Accès libre
    3-D groundwater modeling at regional scale
    (2001)
    Kimmeier, Francesco
    ;
    ;
    Király, László
    Large hydrogeological basins are constituted of several superimposed aquifers, separated by geological formations of relatively low permeabilities. The delimitation of the different flow systems is far more difficult to realize for a heterogeneous system. Flux vectors provide valuable indications about groundwater flow paths and hydraulic exchanges between the different geological formations. Hydraulic relationships between two superimposed aquifers can vary locally: an aquifer can «feed» the underlying one at some point and conversely elsewhere. These relationships, which constitute in fact the flow field, will be determined by the structure of the basin as defined by the spatial distribution of the rock permeabilities, and by the boundary conditions, as defined by the locations of the recharge and discharge areas. The aim of this study is to show schematically the deep groundwater flow patterns between the massives of the Aar and the Black Forest. The hydrogeological profiles illustrate three-dimensional flow fields inside a large volume of terrain and represent but one of the numerous solutions of the mathematical modelling realized. Computations have been performed for a steady state flow regime, which means that the boundary conditions do not vary with time.
    On the basis of modelling results, it was possible to illustrate schematically the deep flow systems of the most important aquifers between the Aar massives and the Black Forest (Malm, Muschelkalk and upper Cristallin). An approximate but plausible representation of the groundwater circulation in deep aquifers was obtained thanks to the model. We are able to distinguish between the hydraulic relationships of two superimposed aquifers in various regions. The three-dimensional representation shows the outcrop zones of the different geological formations as well as the situation of recharge areas, which are characterised by high potentials, and discharge zones, which are characterised by low potentials in valleys represented by the hydrographic network.
    Modelling results are then compared to available measurements in an attempt to validate the results. It is interesting to notice that it was possible, to a certain extent, to verify the modelling results by deep drillings. Most particularly, measurements of the hydraulic potentials at various depths in these boreholes have revealed upwellings close to the regional discharge areas.
  • Publication
    Accès libre
    Eléments hydrogéologiques dans l’étude de l’influence de deux décharges sur le système aquifère de la plaine du Rhône (Valais central, Suisse)
    Ebener, Steeve
    ;
    ;
    Wildi, Walter
    Hydrogeological elements in the study of the influence of two landfills on the Rhône plain aquifer system (central Valais, Switzerland). – The aim of this publication is to contribute to the knowledge of a part of the Rhône plain alluvial system under the influence of two landfills.
    The hydrological environment of this zone is described using topographic, geologic, climatic and hydrologic information, allowing a 3D approach.
    This analysis confirms the complexity of the ground water flows in the aquifer between Sierre and Granges. The great diversity of the anthropogenic or natural element sources are responsible for the 3D heterogeneity of the water quality observed in the aquifer.
  • Publication
    Accès libre
    Drought risk analysis applied to porous Swiss aquifers
    Kimmeier, Francesco
    ;
    ;
    Eisenlohr, Laurent
    ;
    Rossier, Yvan
    The impact of hydrogeological drought on groundwater has been studied in the context of natural flow systems. The aim of this article is to find the relative resistance of 18 unconfined aquifer systems in porous media to a prolonged shortfall in recharge. A synthetic relative drought resistance indicator has been calculated for each of the aquifer systems based on 4 variables which are the half-recession time, the specific regulatory capacity, the drainage density and the aquifer system area.
    The analysis shows that 33% of the chosen aquifer systems are weakly resistant. By contrast, 22% have a high drought resistance. The other aquifer systems are of moderate resistance (22%) or of good resistance (22%).
  • Publication
    Accès libre
    Contribution of a GIS in the spatial modeling of the hydrologic balance of Allondon watershed (France, Switzerland)
    Ebener, Steeve
    ;
    Wildi, Walter
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    ;
    Jaquet, J-M
    ;
    Fortin, J.-P
    This paper discusses the development of an approach allowing the spatial distribution of the hydrologic balance at the watershed scale using Geographical Information Systems (GIS). Methods were developed in order to obtain the intensity distribution of precipitation, interception, infiltration, runoff and evapotranspiration. These methods have been applied on the Allondon watershed (France, Switzerland). At the scale of this watershed (142 km2), the annual input of rain reaches 190*106m3, the snow melt contributing to 4*106m3 to this amount. Vegetation intercepts 26*106m3 from which 8*106m3 aren’t evapotranspired but reaching the ground. On the ground surface, 176*106m3 are divided into runoff for 92*106m3 and infiltration for 84*106m3. The evapotranspiration generates a return of 61*106m3 in the atmosphere. This volume of water comes from interception and from the stock observed in the soils.
  • Publication
    Accès libre
    Three-dimensional GIS cartography applied to the study of the spatial variation of soil horizons in a Swiss floodplain
    Santos Mendonça, M.L
    ;
    Guenat, Claire
    ;
    ;
    Golay, Frederic
    In this study, we propose to establish a framework for the study of the spatial variability of the soils found in the floodplain of the Sarine River and for the visualisation of soil distribution patterns in two- and three-dimensions (2-D, 3-D). This environment is characterised by a large lateral and vertical spatial variability of soils that corresponds to the temporal and spatial variations of the fluvial dynamics of the Sarine. The study was carried out using existing Geographical Information System (GIS) functions combined with applications specific to soil cartography. This particular GIS cartography is based on the notion of the soil horizon instead of that of the soil diagnostic profile. A Global Positioning System (GPS) survey was carried out in order to construct a local Digital Elevation Model (DEM) and to ascertain the spatial coordinates for each of the 181 soil obsevation locations. All data were stored in a GIS database, and both landform modeling and soil cartography was undertaken. GIS, ARC/INFO, and Vertical Mapper for MapInfo were adequate for our linear triangulation interpolation, for contour processing and for the creation of cross-sections as well as the corresponding vertical profiles. These vertical profiles served to illustrate the superposition of soil horizons along any line across the sampled area. A 3-D representation of soil was obtained using the quadratic finite-element method, which is generally employed in geological studies and which we adapted especially for the representation of soil horizons. 3-D cartography of this type allows the spatial pattern of a given horizon — including the variation of its thickness, the superimposition of the different soil horizons, the total soil depth, and the number of horizons at any given location — to be followed through space. Our approach, furthermore, facilitates the perception of soil horizons and their juxtarelationships as 3-D objects, and permits the visualisation of the relationships that exist between any given horizon (or sequence of horizons) and the surface topography. In thus enabling the realistic representation and easy visualisation of the spatial distribution and variability of soils in the landscape, our methodological approach provides a powerful instrument for soil scientists, and a useful decision-support tool for ecosystem management.