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Bouzelboudjen, Mahmoud

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Bouzelboudjen, Mahmoud
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https://libra.unine.ch/handle/123456789/1079

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  • Publication
    Accès libre
    3-D groundwater modeling at regional scale
    (2001)
    Kimmeier, Francesco
    ;
    Bouzelboudjen, Mahmoud 
    ;
    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
    TracES/View - Traçage des Eaux Souterraines : Application SIG en milieu karstique jurassien (Suisse)
    Bouzelboudjen, Mahmoud 
    ;
    Ornstein, Pascal
    ;
    Kimmeier, Francesco
    L'usage de traceurs artificiels est une méthode spécialement bien établie pour étudier les aquifères karstiques. Dans ce contexte, les traçages (avec des traceurs artificiels et biologiques) permettent de déterminer les limites des bassins versants, d'identifier la relation entre une perte et une résurgence, d'évaluer les phénomènes de diffluence, de déterminer le temps de transit, etc. Plus récemment les méthodes de traçage sont utilisées dans les études quantitatives de transport de polluant. Les essais de traçage prenant du temps et étant coûteux, une application (TracES/View) combinant les Systèmes d'Informations Géographiques (SIG) ArcInfo et ArcView, les deux couplés avec une base de données MS Access a été développée afin de planifier de façon efficace la réalisation de nouveaux essais de traçage. Une application utilisant ArcView, développée avec le language de programmation orienté-objets Avenue permet à des non-spécialistes en SIG d'accéder facilement aux éléments de la base de données des essais de traçage d'une manière graphique intuitive et interactive à l'écran. Utilisée conjointement avec d'autres cartes thématiques (la topographie, les surfaces structurales des formations géologiques, la délimitation des aquifères, les perméabilités, l'utilisation du sol, etc.), elle peut fournir un outil puissant d'aide à la décision pour la gestion des ressources en eaux souterraines., The use of artificial tracers is a specially well-established method to investigate karstic aquifers. In this case, tracing (artificial and biological tracers) enables to delimit watercatchment boundaries, to identify relation between a sinkhole and an outlet, to assess diffluent phenomena, transit time, etc. More recently tracer methods have been used in pollution transport studies. Tracer studies being time-consuming and expensive, an application (TracES/View) combining ArcInfo and ArcView Geographical Information Systems (GIS), both coupled with MSAccess database has been developped to provide an efficient way to plan the implementation and the planning of new tracer tests. An ArcView application developped with Avenue object-oriented scripting language allows GIS non-specialists to easily access data from tracer tests database in an interactive and intuitive way. Used in conjunction with other thematic maps (hydraulic conductivity, landuse, groundwater resources, and so on), it can provide a powerful decision-support tool for groundwater resources management.
  • Publication
    Accès libre
    Geohydrological parameters identification and groundwater vulnerability to pollution: A Swiss case study
    Kimmeier, Francesco
    ;
    Bouzelboudjen, Mahmoud 
    ;
    Ornstein, Pascal
    ;
    Weber, Isabelle
    ;
    Rouiller, Jean-Daniel
    The alluvial aquifer of the Rhône valley in Switzerland, which extends over 110 km and occupies an area of 256 km2, is of great economic importance. Its groundwaters are easily accessible and thus exploitable at low cost. However, its location in an often narrow valley with intense human activity (industry, agriculture, communications network) makes it particularly vulnerable from both a qualitative (industrial and\or agricultural pollution) and quantitative point of view (groundwater flow disturbance following civil engineering works). Since 1995, the Swiss canton of Valais has decided to compile datasets from a number of local studies (water supply, hydro-electricity, and geotechnical studies) into a regional, integrated hydrogeological framework. The realization of the study has shown the importance of GIS tool either for the computing and mapping of the first piezometric map between Brig and Léman Lake or the elaboration of vulnerability maps. The geostatistic tool was also intensively used all over the spatial treatment of data. The comparison of groundwaters NO3-- content (1985 and 1995), has shown that globally the nitrates content in the groundwater is low (< 30 mg/l for 90 % of samples). However it must be notice that the evolution of the NO3-- content degrades during time. The study of vulnerability to pollution for the aquifer situated between Sierre and Vétroz as shown significant differences between the four different methods used. As main results DRASTIC and SINTACS integrated methods are concentrated between Moderate and High vulnerability when NLFB and GOD intrinsic methods are concentrated between Very Low and Moderate vulnerability. Intrinsic methods have the tendency to minimize the vulnerability.
  • Publication
    Accès libre
    A statistical time series analysis of hydro-climatic stress on karst aquifer system (Switzerland)
    Kimmeier, Francesco
    ;
    Bouzelboudjen, Mahmoud 
    ;
    Eisenlohr, Laurent
    ;
    Rossier, Yvan
    ;
    Zwahlen, François 
    In order to determine the impact of climatic variations on several spring discharge, five karst aquifer systems were chosen in the Neuchâtel Jura (three basins over an area of 359 km2) and in the Prealps (2 basins of 4 and 10 km2 respectively). The records of air temperature, precipitation and groundwater discharge vary between 13 and 91 years. Statistical trend analyses (Kendall and Spearman tests) and correlation and spectral analyses have been used to analyze these records. The aim of this paper is not to generalize the results to all karstic aquifers in Switzerland but to answer the three following questions : (i) is there a trend at a given station for given parameters ?, (ii) are the trends the same for the different stations ?, (iii) and finally can we detect the impact of possible climatic changes on the natural responses of five karst springs in the Jura and Prealps ? For the Neuchâtel Jura, a regional trend of rising air temperature has been demonstrated. This is marked by two successive increases in 1945 and 1980. In the Prealps of Vaud, this trend is less well defined. Only the increase in the 1980's has been locally detected. The statistical study of precipitation shows its random character at the regional scale of the Neuchâtel Jura and Prealps. The trend of a reduction in groundwater discharge at Champs-du-Moulin in the Areuse basin is visible since 1945. It is part of a regional trend towards lower discharge, no trend has been observed at the La Doux and Noiraigue Springs. In the Prealps, a rising trend has been observed at Les Avants Spring since 1976 and a falling trend in discharge can be identified at Grandchamp Spring since 1988. Despite the fact that in certain cases, there has been a coincidence between the beginning of temperature increase and of falling discharge, the trends shown do not allow us to state that the only cause is that of climatic changes.
  • Publication
    Accès libre
    GIS Vector and Raster Database, Advanced Geostatistics and 3-D Groundwater Flow Modelling in Strongly Heterogeneous Geologic Media: An Integrated Approach
    Bouzelboudjen, Mahmoud 
    ;
    Kimmeier, Francesco
    The aquifers of the Rhône valley in Switzerland are of great economic importance. The groundwaters are exploitable at slight costs. However, their situation make them specially vulnerable. The aim of this paper is to give a brief outlook on the methodology to build a very powerful three dimensional hydrogeological model. This model will be used by the community of Valais as a tool for the management and protection of the groundwater. ArcInfo [9] and ArcView [10] are employed as geographic information system and Oracle [15] and Access [1] as database management system on workstation and personal computer. The advanced geostatistical treatment of spatial basic data is carried out through several techniques (Surfer [17], Isatis [11] and ArcInfo). The 3-D hydrogeological mathematical model are based on the finite element method (Feflow [7] and FEN derived from FEM 301 [14]).
  • Publication
    Accès libre
    Travel path uncertainty: a case study combining stochastic and deterministic hydrodynamic models in the Rhône valley, Switzerland
    Kimmeier, Francesco
    ;
    Bouzelboudjen, Mahmoud 
    ;
    Ababou, Rachid
    ;
    Ribeiro, Luis
    In the framework of waste storage in geological formations at shallow or greater depths and accidental pollution, the numerical simulation of groundwater flow and contaminant transport represents an important instrument to predict and quantify the pollution as a function of time and space. The numerical simulation problem, and the required hydrogeologic data, are often approached in a deterministic fashion. However, deterministic models do not allow to evaluate the uncertainty of results. Furthermore, the hydrogeologic data and hydrodynamic properties required to implement the flow-transport model are generally very scant, so that an essential part of the simulation effort needs to be devoted to building the different spatially distributed data through spatial interpolation, extrapolation, smoothing, etc. In this paper, deterministic (classic finite element hydrodynamic model) and stochastic approaches (geostatistics : kriging and conditional simulations) are used for evaluating groundwater flow patterns and pollutant trajectories for a site-specific application (Rhône valley aquifer in Switzerland, area of 6.5 km2). The stochastic approach, based on kriging and multiple conditional simulations, leads to a quantification of uncertainty of flow-transport simulations, which are due to the underlying uncertainty of hydrogeologic properties and their spatial distribution. The available data used in this case study are : 55 transmissivity, 791 permeability and 145 hydraulic potential values. In spite of the relative wealth of available data, our study shows that the uncertainty of pollutant migration pathlines and travel distances is relatively important. The distance traveled by a pollutant particle during 30 monthes varies between 3150 m and 4800 m over five different but equally plausible scenarios (conditional simulations). The uncertainty is about 42% relative to the average travel distance, or 55% relative to the smallest travel distance mentioned above.
  • Publication
    Accès libre
    Drought risk analysis applied to porous Swiss aquifers
    Kimmeier, Francesco
    ;
    Bouzelboudjen, Mahmoud 
    ;
    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%).