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See detailAppui à la gestion et à la protection des ressources en eaux souterraines exploitées dans la région de Bobo Dioulasso (Burkina Faso) – mise en place d’une base de données spatiales
Sauret, Elie ULg; Gardin, Nicolas; Kam, Ahmed et al

Conference (2011, November 03)

Située au sud ouest du Burkina Faso, dans la région de Bobo Dioulasso, le bassin du kou couvre 1860km2 de superficie et héberge d’énormes réservoirs en eau souterraines auxquels sont associés ... [more ▼]

Située au sud ouest du Burkina Faso, dans la région de Bobo Dioulasso, le bassin du kou couvre 1860km2 de superficie et héberge d’énormes réservoirs en eau souterraines auxquels sont associés d’importantes sources diffuses. Ces réserves en eau sont sollicitées pour l’alimentation en eau de boisson, l’industrie, l’agriculture irriguée et l’élevage ; elles ont été et demeure l’objet de nombreuses études touchant l’ingénierie de l’eau et des sols, l’imagerie satellitaire et géophysique, l’hydrochimie…. Depuis 2005, le projet de coopération bilatérale entre la WBI1 et le MAHRH-BF2 dénommé : « Appui à la gestion et à la protection des ressources en eaux souterraines exploitées dans la région de Bobo – Dioulasso » a permis de collecter, compiler et archiver des données (numériques, papiers, cartes…) qui ont servi à la construction d’une base de données spatiales couplées à un SIG (ArcGis). Des post-traitements de ces données ont permis l’établissement de cartes thématiques sur les ressources en eau de la région : carte hydrogéologique, carte de la vulnérabilité intrinsèque des aquifères souterrains, carte hydrogéomorphologique…….Utilisée au sein du projet pour les travaux de thèse en cours, la GDB des ressources en eau du bassin du Kou est largement vulgarisée et diffusée à l’échelle régionale et nationale aux utilisateurs et acteurs du domaine de l’eau. [less ▲]

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See detailApplication of the HFEMC method to an abandoned coalfield in Belgium: From conceptualisation to scenario simulations
Wildemeersch, Samuel ULg; Brouyère, Serge ULg; Orban, Philippe ULg et al

Conference (2009, October 20)

The Hybrid Finite Element Mixing Cell (HFEMC) method is a flexible modelling technique particularly suited to mining context (Brouyère et al., 2009). The principle of this method is to subdivide the ... [more ▼]

The Hybrid Finite Element Mixing Cell (HFEMC) method is a flexible modelling technique particularly suited to mining context (Brouyère et al., 2009). The principle of this method is to subdivide the modelled zone into several subdomains and to select a specific equation, ranging from the simple linear reservoir equation to the groundwater flow in porous media equation, to model groundwater flow in each subdomain. The model can be run in transient conditions, which makes it a useful tool for managing mine closure post-issues such as groundwater rebound and water inrushes. An application of the HFEMC method to an abandoned underground coal mine near the city of Liège (Belgium) is presented. The case study zone has been discretized taking advantage of the flexibility of the method. Then, the model has been calibrated in both steady-state and transient flow regimes based on hydraulic head and water discharge rate observations. Finally, the calibrated model has been used to run several scenarios in order to assess the impacts of possible future phenomena on the hydraulic heads and the water discharge rates. Among others, the simulation of a strong rainfall event shows a quick and strong increase in hydraulic heads in some exploited zones coupled with a strong increase in associated water discharge rates. This could lead to stability problems in the hill slopes near the exploited zones. This kind of predictions can greatly help managing and predicting mine water problems in this particularly complex mining system. [less ▲]

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See detailProspection géophysique de la nappe alluviale dans la région de Nasso, Bodo – Dioulasso (Burkina Faso)
Beaujean, Jean ULg; Nguyen, Frédéric ULg; Sauret, Elie ULg et al

Report (2009)

Afin d’appuyer la gestion et la protection des ressources en eaux souterraines au Burkina Faso, dans la région de Bobo-Dioulasso, une mission géophysique relative à la caractérisation du site de la plaine ... [more ▼]

Afin d’appuyer la gestion et la protection des ressources en eaux souterraines au Burkina Faso, dans la région de Bobo-Dioulasso, une mission géophysique relative à la caractérisation du site de la plaine alluviale dans la localité de Nasso a été effectuée. Plusieurs méthodes géophysiques ont été employées afin de déterminer l’hétérogénéité des terrains superficiels, l’épaisseur de la nappe alluviale, ainsi que la profondeur du bedrock. Les trois méthodes déployées pour atteindre ces objectifs sont la tomographie électrique, le bruit de fond H/V, et le radar géologique. Ce dernier n’a pas donné de résultats satisfaisant tandis que les deux autres méthodes se sont montrées concluantes pour déterminer la profondeur du bedrock et détecter des hétérogénéités dans les terrains superficiels et profonds. [less ▲]

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See detailGround water flow simulation in mining works: Application of the Hybrid Finite Element Mixing Cell method
Wildemeersch, Samuel ULg; Orban, Philippe ULg; Brouyère, Serge ULg et al

Conference (2009, April 22)

Hydrogeological models can greatly help simulating groundwater flow in the particular context of mining works. However, classical modeling techniques are not so suited in this context because the medium ... [more ▼]

Hydrogeological models can greatly help simulating groundwater flow in the particular context of mining works. However, classical modeling techniques are not so suited in this context because the medium is strongly disturbed by shafts and networks of galleries. Consequently, specific modeling techniques have been developed. Box model techniques require only few parameters but they calculate only mean water levels in exploited zones and do not consider interactions between exploited and unexploited zones. Conversely, physically-based and spatially-distributed techniques represent explicitly both exploited and unexploited zones and take into account interactions between them but they require a lot of parameters sometimes difficult to estimate. The Hybrid Finite Element Mixing Cell (HFEMC) method is a new modeling technique constituting a compromise between simple and complex techniques used in mining context. The principle of this method is to fully couple a representation of exploited zones by a group of mixing cells possibly interconnected by pipes and a representation of unexploited zones by classical finite elements. Interactions between mixing cells and finite elements of the mesh are taken into account through 3rd type (Fourier) internal boundary conditions. With this method, exploited zones are characterized by mean water levels while spatially-distributed hydraulic heads are calculated for the entire adjacent and overlaying unexploited zones. Additionally, thanks to the coupling between mixing cells and finite elements, water exchanges between exploited and unexploited zones are explicitly taken into account. The HFEMC method allows also simulating groundwater rebound following mine closure and associated phenomena such as water inrushes. Concepts and equations of the HFEMC method are presented and illustrated using test cases. First results of an application on an abandoned coalfield in the region of Liege (Belgium) are also proposed. [less ▲]

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See detailThe Hybrid Finite Element Mixing Cell Method: A New Flexible Method for Modelling Mine Ground Water Problems
Brouyère, Serge ULg; Orban, Philippe ULg; Wildemeersch, Samuel ULg et al

in Mine Water & the Environment (2009), 28(2), 102-114

Dewatering operations often stop at mine closure. The ground water rebound can have undesirable consequences, which numerical models can help one understand and manage. However, classical modelling ... [more ▼]

Dewatering operations often stop at mine closure. The ground water rebound can have undesirable consequences, which numerical models can help one understand and manage. However, classical modelling techniques are relatively unsuitable to these contexts. While spatially-distributed and physically-based models suffer difficulties due to the lack of data and the complexity of geological and hydrogeological conditions, black-box models are too simple to deal with the problems effectively. A new modelling method is proposed to simulate ground water environments in which water flows through mined (exploited) and unmined (unexploited) areas. Exploited zones are simulated using a group of mixing cells possibly interconnected by pipes. Unexploited zones are simultaneously simulated using classical finite elements. This combined approach allows explicit calculation of ground water flows around the mine and mean water levels in the exploited zones. Water exchanges between exploited zones and unexploited zones are simulated in the model using specifically-defined internal boundary conditions. The method is tested on synthetic cases of increasing complexity, and first results from a real case study are presented. [less ▲]

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See detailDL 44 : Methodology and setup of the adopted groundwater vulnerability assessment method
Beaujean, Jean ULg; Wojda, Piotr; Gardin, Nicolas et al

Report (2008)

The objectives of this deliverable DL44 are to finalize the description of the global groundwater vulnerability assessment methodology, in particular : (1) to propose an extension of the concept of ... [more ▼]

The objectives of this deliverable DL44 are to finalize the description of the global groundwater vulnerability assessment methodology, in particular : (1) to propose an extension of the concept of sensitivity coefficient to vulnerability coefficient by introducing a ratio (distance to damage ratio) that reflects the “distance” between the current state of degradation of the water resource system and the “damaged state”,(2) To describe the methodology proposed to combine, through aggregation of spatiallydistributed indicators and multi criteria analysis, the different vulnerability coefficientsinto a single indicator of groundwater vulnerability for decision making, (3) To go further into the analysis and discussion of several key theoretical “case studies” for illustrating the way to setup the full methodology, from the DPSIR analysis to the expression of sensitivity and vulnerability coefficients. [less ▲]

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See detailPromouvoir des approches innovantes de recherche-développement en matière de GIRE au Burkina Faso
Wellens, Joost ULg; Diallo, Mamadou; Gardin, Nicolas et al

in Global Water Partnership - Toolbox: Integrated Water Resources Management (2008), CS 322

Le bassin du Kou, situé dans le sud-ouest du Burkina Faso, est depuis quelques décennies le théâtre de différentes formes de conflits liés à toute une série de problèmes que l’on rencontre généralement ... [more ▼]

Le bassin du Kou, situé dans le sud-ouest du Burkina Faso, est depuis quelques décennies le théâtre de différentes formes de conflits liés à toute une série de problèmes que l’on rencontre généralement dans des zones irriguées. Dans le bassin du Kou, les aménagements hydro-agricoles couvrent un e superficie totale de près de 2.000 ha ; il s’agit des périmètres privés maraîchères et horticoles, et d’un grand périmètre de 1.200 ha réalisé par l’Etat. Malgré la présence de sources importantes, d’une nappe phréatique facilement exploitable et d’un cours d’eau pérenne, la plupart des utilisateurs se retrouvent régulièrement confrontées à des pénuries d’eau résultant d’une extension de l’agriculture irriguée. Depuis 1987 les autorités politiques et administratives ont entrepris de rechercher avec les usagers concernés les voies pour circonscrire les menaces résultant de cette situation par la création d’un Comité ‘provisoire’ de Gestion du Bassin du Kou (CGBK). Malgré l’imagination dont il a fait preuve et les nombreuses réalisations à son actif, il aura fallu attendre l’année 2008 pour voir la naissance d’un Comité Local de l’Eau (CLE), inspiré des expériences du CGBK. Celui-ci s’inscrit dans le cadre d’une GIRE décentralisée voulue par l’Etat burkinabé. La particularité de ce CLE est la montée en puissance en son sein de l’action de la société civile. Cette dernière s’est engagée à la mise en chantier d’une innovation institutionnelle: un Observatoire de l’Eau (OE). Il a pour vocation d’appuyer les pouvoirs publics dans le développement de programmes ’études relatifs à la gestion des ressources en eau. A travers l’élaboration d’une base de données spatialisée, l’OE se concentre sur la mise en place d’outils de contrôle et de suivi des ressources en eau et de leur exploitation. Les outils et études développés sont restitués et discutés lors des réunions du CLE. Il s permettent au CLE de mieux prévoir des futurs conflits liés à l’eau et servent également comme outil d’arbitrage. [less ▲]

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See detailThe Hybrid Finite-Element Mixing-Cell method: a new flexible method for modelling mine water problems
Brouyère, Serge ULg; Orban, Philippe ULg; Wildemeersch, Samuel ULg et al

in Rapantova, N.; Hrkal, Z. (Eds.) Mine Water and the Environment Proceedings of IWMA 2008 (2008)

Mine closure is often accompanied by a stop in dewatering operations. This generally induces groundwater rebound in the mined rock system with short and long term consequences that may be disastrous: soil ... [more ▼]

Mine closure is often accompanied by a stop in dewatering operations. This generally induces groundwater rebound in the mined rock system with short and long term consequences that may be disastrous: soil instabilities such as landslides and subsidence reactivation, flooding, flooded basement and acid mine drainage. Modelling tools can be very advantageous and efficient in helping understanding and managing such problems, however, classical modelling approaches have proved to be relatively unsuited to such contexts. Because of the former mining operations, the underground geological system is strongly disturbed (excavated, fractured and collapsed zones, galleries, large shafts, etc.). Using complex spatially distributed modelling approaches such as 3D finite elements usually lead to strong difficulties related to the lack of data, the complexity of geological and hydrogeological conditions (complex geometry, non Darcian fluxes…). On the other hand, using a simplified approach such as black-box models often leads to oversimplification of the reality: particularly when interactions between the mined system and its surrounding geological and hydrogeological environment are very important. A new modelling approach is developed for simulation of the groundwater flow in such complex environments. It combines, in a single fully integrated simulator, a representation of the unmined area by a classical finite element modelling technique, together with conceptualisation of the worked areas and galleries by a group of mixing cells connected by pipes. The whole assembled groundwater flow model allows an accurate estimation and representation of (a) water infiltration (precipitations, river losses …) through the unsaturated zone reaching the exploited area (recharge of boxes) and (b) water exchanges with adjacent aquifers. The model can estimate the flow of groundwater in and around the minefield and the mean water level in the boxes. It is also capable of considering water exchanges between different mined zones, through connection pathways such as old roadways galleries and shafts. Modelling concepts and equations are described and illustrated using basic and advances validation examples. A real case application corresponding to an abandoned coalfield in the region of Liège (Belgium) is used to illustrate the suitability and efficiency of the approach. [less ▲]

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See detailGroundwater vulnerability assessment using physically based modelling: from challenges to pragmatic solutions
Popescu, Ileana Cristina; Gardin, Nicolas; Brouyère, Serge ULg et al

in Refsgaard, J. C.; Kovar, K.; Haarder, E. (Eds.) et al Calibration and Reliability in Groundwater Modelling: Credibility in Modelling (2008)

Numerous groundwater vulnerability and risk mapping techniques have been developed taking into consideration a variable number of factors. The most common techniques are based on calculation of an index ... [more ▼]

Numerous groundwater vulnerability and risk mapping techniques have been developed taking into consideration a variable number of factors. The most common techniques are based on calculation of an index expressing the protective effect of underground formations overlying the groundwater resource. The limitation of most of these methods is related to their use of a qualitative definition of groundwater vulnerability, as opposed to a definition based on a quantitative description of contaminant migration. A physically-based point of view and definition of the vulnerability is proposed and based on three factors describing a pollution event, which are the contaminant transfer time from the hazard location to the 'target', the contamination duration at the 'target' and the level of contaminant concentration reached at the 'target'. This concept allows a clear distinction between conventional aspects and physically-based results in the building of a final vulnerability indicator. This methodology has the further advantage to consider the possible impact of runoff conditions occurring at the land surface and possibly leading to lateral contamination of groundwater through downstream preferential infiltration features. Practically, this method needs to describe and simulate the pollutant migration in the unsaturated zone and possibly in the saturated zone in order to assess the breakthrough curve at the 'target'. Preliminary application is illustrated on a case-study located in a limestone basin in Belgium. Perspectives are proposed towards a generalisation of the vulnerability concept for risk assessment within a pressure - state - impact framework. [less ▲]

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See detailStress factors and associated physically based criteria and conclusions on the directions to be followed for developing a physically based vulnerability assessment method
Gardin, Nicolas; Wojda, Piotr; Brouyère, Serge ULg

Report (2005)

The specific results and outcomes of this deliverable is the proposition of a methodological framework for groundwater vulnerability assessment to any kind of stress factors, from a physically-based point ... [more ▼]

The specific results and outcomes of this deliverable is the proposition of a methodological framework for groundwater vulnerability assessment to any kind of stress factors, from a physically-based point of view. This methodology is in addition compatible with the well-known EU DPSIR framework for analysis from a physical and socio-economical perspective, environmental problems. From a more generic perspective, this deliverable provides a very convenient and rigorous framework for integrating the various research components developed within the project, into a decision support system, integrating environmental problems, data, processes and models, and socio-economical aspects. [less ▲]

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